Empire State Realty Trust (ESRT) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 22, 2018	Jun. 30, 2017
Entity Registrant Name	Empire State Realty Trust, Inc.
Entity Central Index Key	1,541,401
Document Type	10-K
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Common Class A [Member]
Entity Common Stock, Shares Outstanding		161,824,457
Entity Public Float			$ 3,271,130,000
Common Class B [Member]
Entity Common Stock, Shares Outstanding		1,049,276

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commercial real estate properties, at cost:
Land	$ 201,196	$ 201,196
Development costs	7,986	7,951
Building and improvements	2,458,473	2,249,482
Commercial real estate properties, at cost, gross	2,667,655	2,458,629
Less: accumulated depreciation	(656,900)	(556,546)
Commercial real estate properties, net	2,010,755	1,902,083
Cash and cash equivalents	464,344	554,371
Restricted cash	65,853	61,514
Tenant and other receivables, net of allowance of $1,422 and $3,333 in 2017 and 2016, respectively	28,329	22,542
Deferred rent receivables, net of allowance of $185 and $390 in 2017 and 2016, respectively	178,629	152,074
Prepaid expenses and other assets	61,028	53,749
Deferred costs, net	262,701	277,081
Acquired below market ground leases, net	368,229	376,060
Goodwill	491,479	491,479
Total assets	3,931,347	3,890,953
Liabilities:
Mortgage notes payable, net	717,164	759,016
Senior unsecured notes, net	707,895	590,388
Unsecured term loan facility, net	263,662	262,927
Unsecured revolving credit facility	0	0
Accounts payable and accrued expenses	110,849	134,064
Acquired below market leases, net	66,047	82,300
Deferred revenue and other liabilities	40,907	32,212
Tenants’ security deposits	47,086	47,183
Total liabilities	1,953,610	1,908,090
Commitments and contingencies
Empire State Realty Trust, Inc. stockholders' equity:
Preferred stock, $0.01 par value per share, 50,000,000 shares authorized, none issued or outstanding	0	0
Additional paid-in capital	1,128,460	1,104,463
Accumulated other comprehensive loss	(8,555)	(2,789)
Retained earnings	46,762	50,904
Total Empire State Realty Trust, Inc.'s stockholders' equity	1,168,282	1,154,136
Non-controlling interests in operating partnership	801,451	820,723
Private perpetual preferred units, $16.62 per unit liquidation preference, 1,560,360 issued and outstanding in 2017 and 2016	8,004	8,004
Total equity	1,977,737	1,982,863
Total liabilities and equity	3,931,347	3,890,953
Common Class A [Member]
Empire State Realty Trust, Inc. stockholders' equity:
Common stock	1,604	1,547
Common Class B [Member]
Empire State Realty Trust, Inc. stockholders' equity:
Common stock	$ 11	$ 11

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Tenant and other receivables allowance	$ 1,422	$ 3,333
Deferred rent receivables allowance	$ 185	$ 390
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Private perpetual preferred units, liquidation preference per share (in dollars per share)	$ 16.62	$ 16.62
Private perpetual preferred units, issued, shares	1,560,360	1,560,360
Private perpetual preferred units, outstanding, shares	1,560,360	1,560,360
Common Class A [Member]
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	160,424,575	154,744,740
Common stock, shares outstanding (in shares)	160,424,575	154,744,740
Common Class B [Member]
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	1,052,469	1,095,737
Common stock, shares outstanding (in shares)	1,052,469	1,095,737

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Rental revenue													$ 483,944	$ 460,653	$ 447,784
Tenant expense reimbursement													73,679	73,459	79,516
Observatory revenue													127,118	124,814	112,172
Construction revenue													0	0	1,981
Third-party management and other fees													1,400	1,766	2,133
Other revenue and fees													26,327	17,308	14,048
Total revenues	$ 183,070	$ 187,320	$ 177,124	$ 164,954	$ 179,263	$ 175,848	$ 165,815	$ 157,074	$ 165,200	$ 175,779	$ 164,773	$ 151,882	712,468	678,000	657,634
Operating expenses:
Property operating expenses													163,531	153,850	158,638
Ground rent expenses													9,326	9,326	9,326
General and administrative expenses													50,315	49,078	38,073
Observatory expenses													30,275	29,833	32,174
Construction expenses													0	0	3,222
Real estate taxes													102,466	96,061	93,165
Acquisition expenses													0	98	193
Depreciation and amortization													160,710	155,211	171,474
Total operating expenses													516,623	493,457	506,265
Total operating income (loss)	50,964	56,781	51,434	36,666	52,651	53,586	44,192	34,114	37,230	45,343	45,039	23,757	195,845	184,543	151,369
Interest expense													(68,473)	(70,595)	(65,743)
Loss on early extinguishment of debt													(2,157)	(552)	(1,749)
Loss from derivative financial instruments													(289)	0	0
Income before income taxes													124,926	113,396	83,877
Income tax expense													(6,673)	(6,146)	(3,949)
Net income	$ 32,260	$ 35,489	$ 31,359	$ 19,145	$ 33,008	$ 32,897	$ 24,640	$ 16,705	$ 19,370	$ 26,085	$ 26,585	$ 7,888	118,253	107,250	79,928
Private perpetual preferred unit distributions													(936)	(936)	(936)
Net income attributable to non-controlling interests													(54,670)	(54,858)	(45,262)
Net income attributable to common stockholders													$ 62,647	$ 51,456	$ 33,730
Total weighted average shares:
Basic (in shares)													158,380	133,881	114,245
Diluted (in shares)													298,049	277,568	266,621
Net income per share attributable to common stockholders:
Basic (USD per share)													$ 0.40	$ 0.38	$ 0.30
Diluted (USD per share)													$ 0.39	$ 0.38	$ 0.29

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 118,253	$ 107,250	$ 79,928
Other comprehensive loss:
Unrealized loss on valuation of interest rate swap agreements	(11,658)	(3,054)	(1,922)
Amount reclassified into interest expense	1,142	0	0
Other comprehensive loss	(10,516)	(3,054)	(1,922)
Comprehensive income	107,737	104,196	78,006
Net income attributable to non-controlling interests and private perpetual preferred unitholders	(55,606)	(55,794)	(46,198)
Other comprehensive loss attributable to non-controlling interests	4,901	1,576	1,100
Comprehensive income attributable to common stockholders	$ 57,032	$ 49,978	$ 32,908

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Class A [Member]	Common Class B [Member]	Total Stockholders' Equity [Member]	Common Stock [Member]Common Class A [Member]	Common Stock [Member]Common Class B [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Private Perpetual Preferred Units [Member]
Beginning balance (in shares) at Dec. 31, 2014					106,030,000	1,161,000
Beginning balance at Dec. 31, 2014	$ 1,381,097			$ 468,638	$ 1,060	$ 12	$ 406,853	$ 0	$ 60,713	$ 904,455	$ 8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					12,859,000	(41,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			62,070	$ 129	$ (1)	62,003	(61)		(62,070)
Equity compensation:
LTIP units	5,187									5,187
Restricted stock, net of forfeitures (in shares)					14,000
Restricted stock, net of forfeitures	296			296			296
Dividends and distributions	(91,900)			(39,183)					(39,183)	(51,781)	(936)
Net income	79,928			33,730					33,730	45,262	936
Other comprehensive income (loss)	(1,922)			(822)				(822)		(1,100)
Ending balance (in shares) at Dec. 31, 2015					118,903,000	1,120,000
Ending balance at Dec. 31, 2015	1,372,686			524,729	$ 1,189	$ 11	469,152	(883)	55,260	839,953	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A shares, net of costs (in shares)					29,610,854
Issuance of Class A shares, net of costs	611,206			611,206	$ 296		610,910
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					6,191,000	(24,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			23,678	$ 62	$ 0	24,044	(428)		(23,678)
Equity compensation:
LTIP units	9,372									9,372
Restricted stock, net of forfeitures (in shares)					40,000
Restricted stock, net of forfeitures	357			357			357
Dividends and distributions	(114,954)			(55,812)					(55,812)	(58,206)	(936)
Net income	107,250			51,456					51,456	54,858	936
Other comprehensive income (loss)	(3,054)			(1,478)				(1,478)		(1,576)
Ending balance (in shares) at Dec. 31, 2016		154,744,740	1,095,737		154,745,000	1,096,000
Ending balance at Dec. 31, 2016	1,982,863			1,154,136	$ 1,547	$ 11	1,104,463	(2,789)	50,904	820,723	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					5,659,000	(44,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			23,435	$ 57		23,529	(151)		(23,435)
Equity compensation:
LTIP units	13,632									13,632
Restricted stock, net of forfeitures (in shares)					21,000
Restricted stock, net of forfeitures	468			468			468
Dividends and distributions	(126,963)			(66,789)					(66,789)	(59,238)	(936)
Net income	118,253			62,647					62,647	54,670	936
Other comprehensive income (loss)	(10,516)			(5,615)				(5,615)		(4,901)
Ending balance (in shares) at Dec. 31, 2017		160,424,575	1,052,469		160,425,000	1,052,000
Ending balance at Dec. 31, 2017	$ 1,977,737			$ 1,168,282	$ 1,604	$ 11	$ 1,128,460	$ (8,555)	$ 46,762	$ 801,451	$ 8,004

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net income	$ 118,253	$ 107,250	$ 79,928
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	160,710	155,211	171,474
Amortization of non-cash items within interest expense	1,039	739	1,698
Amortization of acquired above and below-market leases, net	(5,721)	(8,795)	(19,353)
Amortization of acquired below-market ground leases	7,831	7,831	7,996
Straight-lining of rental revenue	(26,544)	(30,147)	(21,220)
Equity based compensation	14,100	9,729	5,483
Settlement of derivative contracts	(15,695)	0	0
Loss on early extinguishment of debt	2,157	552	1,749
Increase (decrease) in cash flows due to changes in operating assets and liabilities (excluding the effect of acquisitions):
Restricted cash	(2,843)	2,121	2,954
Tenant and other receivables	(5,787)	(3,760)	4,963
Deferred leasing costs	(31,743)	(22,622)	(31,367)
Prepaid expenses and other assets	(7,893)	(3,289)	(1,956)
Accounts payable and accrued expenses	(25,104)	2,939	(2,674)
Deferred revenue and other liabilities	8,695	824	3,512
Net cash provided by operating activities	191,455	218,583	203,187
Cash Flows From Investing Activities
Decrease (increase) in restricted cash for investing activities	(1,592)	538	(119)
Additions to building and improvements	(222,979)	(181,923)	(141,685)
Development costs	(34)	(453)	(512)
Net cash used in investing activities	(224,605)	(181,838)	(142,316)
Cash Flows From Financing Activities
Proceeds from unsecured revolving credit facility	0	50,000	655,000
Repayments of unsecured revolving credit facility	0	(90,000)	(615,000)
Proceeds from mortgage notes payable	315,000	50,000	0
Repayment of mortgage notes payable	(346,615)	(32,305)	(146,918)
Proceeds from senior unsecured notes	115,000	0	350,000
Proceeds from unsecured term loan	0	0	265,000
Repayment of unsecured term loan	(265,000)	0	0
Proceeds from unsecured revolving credit and term loan facility	265,000	0	0
Repayments of secured term loan and credit facility	0	0	(470,000)
Deferred financing costs	(13,299)	(3,006)	(6,100)
Net proceeds from the sale of common stock	0	611,206	0
Private perpetual preferred unit distributions	(936)	(936)	(936)
Dividends paid to common stockholders	(66,789)	(55,812)	(39,183)
Distributions paid to noncontrolling interests in the operating partnership	(59,238)	(58,206)	(51,781)
Net cash provided by (used in) financing activities	(56,877)	470,941	(59,918)
Net increase (decrease) in cash and cash equivalents	(90,027)	507,686	953
Cash and cash equivalents—beginning of period	554,371	46,685	45,732
Cash and cash equivalents—end of period	464,344	554,371	46,685
Supplemental disclosures of cash flow information:
Cash paid for interest	66,911	69,062	64,808
Interest capitalized	459	0	0
Cash paid for income taxes	5,783	6,238	4,465
Non-cash investing and financing activities:
Building and improvements included in accounts payable and accrued expenses	71,769	66,620	51,315
Derivative instruments at fair values included in prepaid expenses and other assets	0	614	0
Derivative instruments at fair values included in accounts payable and accrued expenses	436	5,591	1,922
Conversion of operating partnership units and Class B shares to Class A shares	$ 23,435	$ 23,678	$ 62,003

Description of Business and Org

Description of Business and Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Organization	Description of Business and Organization As used in these consolidated financial statements, unless the context otherwise requires, “we,” “us,” "our," the "company,” and "ESRT" mean Empire State Realty Trust, Inc. and its consolidated subsidiaries. We are a self-administered and self-managed real estate investment trust, or REIT, that owns, manages, operates, acquires and repositions office and retail properties in Manhattan and the greater New York metropolitan area. We were organized as a Maryland corporation on July 29, 2011. As of December 31, 2017 , our total portfolio contained 10.1 million rentable square feet of office and retail space. We owned 14 office properties (including three long-term ground leasehold interest) encompassing approximately 9.4 million rentable square feet of office space. Nine of these properties are located in the midtown Manhattan market and encompass in the aggregate approximately 7.6 million rentable square feet of office space, including the Empire State Building. Our Manhattan office properties also contain an aggregate of 507,395 rentable square feet of premier retail space on their ground floor and/or lower levels. Our remaining five office properties are located in Fairfield County, Connecticut and Westchester County, New York, encompassing in the aggregate approximately 1.9 million rentable square feet. The majority of square footage for these five properties is located in densely populated metropolitan communities with immediate access to mass transportation. Additionally, we have entitled land at the Stamford Transportation Center in Stamford, Connecticut, adjacent to one of our office properties, that will support the development of an approximately 380,000 rentable square foot office building and garage, which we refer to herein as Metro Tower. As of December 31, 2017 , our portfolio also included four standalone retail properties located in Manhattan and two standalone retail properties located in the city center of Westport, Connecticut, encompassing 205,740 rentable square feet in the aggregate. Empire State Realty OP, L.P. (the "operating partnership") holds substantially all of our assets and conducts substantially all of our business. As of December 31, 2017 , we owned approximately 53.8% of the aggregate operating partnership units in our operating partnership. We, as the sole general partner in our operating partnership, have responsibility and discretion in the management and control of our operating partnership, and the limited partners in our operating partnership, in such capacity, have no authority to transact business for, or participate in the management activities of our operating partnership. Accordingly, our operating partnership has been consolidated by us. We elected to be taxed as a REIT and operate in a manner that we believe allows us to qualify as a REIT for federal income tax purposes commencing with our taxable year ended December 31, 2013. We have two entities that elected to be treated as taxable REIT subsidiaries, or TRSs, and are owned by our operating partnership. The TRSs, through several wholly owned limited liability companies, conduct third-party services businesses, which include the Empire State Building Observatory, cleaning services, cafeteria, restaurant and fitness center and asset and property management services.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and with the rules and regulations of the Securities and Exchange Commission (the "SEC") represent our assets and liabilities and operating results. The consolidated financial statements include our accounts and our wholly owned subsidiaries as well as our operating partnership and its subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. We consolidate entities in which we have a controlling financial interest. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, authority to make decisions, and contractual and substantive participating rights of the partners/members as well as whether the entity is a variable interest entity (“VIE”) and we are the primary beneficiary. The primary beneficiary of a VIE is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. The primary beneficiary is required to consolidate the VIE. Our operating partnership, Empire State Realty OP, L.P., is a variable interest entity of our company, Empire State Realty Trust, Inc. As the operating partnership is already consolidated in the financial statements of Empire State Realty Trust, Inc., the identification of this entity as a variable interest entity had no impact on our consolidated financial statements. We will assess the accounting treatment for each investment we may have in the future. This assessment will include a review of each entity’s organizational agreement to determine which party has what rights and whether those rights are protective or participating. For all VIEs, we will review such agreements in order to determine which party has the power to direct the activities that most significantly impact the entity’s economic performance and benefit. In situations where we or our partner could approve, among other things, the annual budget, or leases that cover more than a nominal amount of space relative to the total rentable space at each property, we would not consolidate the investment as we consider these to be substantive participation rights that result in shared power of the activities that would most significantly impact the performance and benefit of such joint venture investment. A non-controlling interest in a consolidated subsidiary is defined as the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to a parent. Non-controlling interests are required to be presented as a separate component of equity in the consolidated balance sheets and in the consolidated statements of income by requiring earnings and other comprehensive income to be attributed to controlling and non-controlling interests. Accounting Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to use estimates and assumptions that in certain circumstances affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Significant items subject to such estimates and assumptions include allocation of the purchase price of acquired real estate properties among tangible and intangible assets, determination of the useful life of real estate properties and other long-lived assets, valuation and impairment analysis of commercial real estate properties and other long-lived assets, estimate of tenant expense reimbursements, estimate of percentage of completion on construction contracts, valuation of the allowance for doubtful accounts, and valuation of derivative instruments, senior unsecured notes, mortgage notes payable, unsecured notes, unsecured revolving credit and term loan facilities, and equity based compensation. These estimates are prepared using management’s best judgment, after considering past, current, and expected events and economic conditions. Actual results could differ from those estimates. Revenue Recognition Rental Revenue Rental revenue includes base rents that each tenant pays in accordance with the terms of its respective lease and is reported on a straight-line basis over the non-cancellable term of the lease which includes the effects of rent steps and rent abatements under the leases. In general, we commence rental revenue recognition when the tenant takes possession of the leased space or controls the physical use of the leased space and the leased space is substantially ready for its intended use. We account for all of our leases as operating leases. Deferred rent receivables, including free rental periods and leasing arrangements allowing for increased base rent payments, are accounted for in a manner that provides an even amount of fixed lease revenues over the respective non-cancellable lease terms. Differences between rental income recognized and amounts due under the respective lease agreements are recognized as an increase or decrease to deferred rent receivables. In addition to base rent, our tenants also generally will pay their pro rata share of increases in real estate taxes and operating expenses for the building over a base year. In some leases, in lieu of paying additional rent based upon increases in building operating expenses, the tenant will pay additional rent based upon increases in an index such as the Consumer Price Index over the index value in effect during a base year, or contain fixed percentage increases over the base rent to cover escalations. We will recognize rental revenue of acquired in-place above- and below-market leases at their fair values over the terms of the respective leases, including, for below-market leases, fixed option renewal periods, if any. Lease cancellation fees are recognized when the fees are determinable, tenant vacancy has occurred, collectability is reasonably assured, we have no continuing obligation to provide services to such former tenants and the payment is not subject to any conditions that must be met or waived. Total lease cancellation fees for the years ended December 31, 2017 , 2016, and 2015 were $13.6 million , $7.7 million , and $2.0 million , respectively. Such fees are included in other revenues and fees in our consolidated statements of income. Observatory Revenue Revenues from the sale of Observatory tickets are recognized upon admission or ticket expirations. Deferred revenue related to unused and unexpired tickets as of December 31, 2017 and 2016 was $4.1 million and $4.1 million , respectively. Gains on Sale of Real Estate We record a gain on sale of real estate when title is conveyed to the buyer and we have no substantial economic involvement with the property. If the sales criteria for the full accrual method are not met, we defer some or all of the gain recognition and account for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery methods, as appropriate, until the sales criteria are met. Third-Party Management and Other Fees We earn revenue arising from contractual agreements with related party entities for asset and property management services. This revenue is recognized as the related services are performed under the respective agreements in place. Advertising and Marketing Costs Advertising and marketing costs are expensed as incurred. The expense for the years ended December 31, 2017 , 2016, and 2015 was $7.6 million , $9.4 million and $8.7 million , respectively, and is included within operating expenses in our consolidated statements of income. Real Estate Properties and Related Intangible Assets Land and buildings and improvements are recorded at cost less accumulated depreciation and amortization. The recorded cost includes cost of acquisitions, development and construction and tenant allowances and improvements. Expenditures for ordinary repairs and maintenance are charged to property operating expense as incurred. Significant replacements and betterments which improve or extend the life of the asset are capitalized. Tenant improvements which improve or extend the life of the asset are capitalized. If a tenant vacates its space prior to the contractual termination of its lease, the unamortized balance of any tenant improvements are written off if they are replaced or have no future value. For developed properties, direct and indirect costs that clearly relate to projects under development are capitalized. Costs include construction costs, professional services such as architectural and legal costs, capitalized interest and direct payroll costs. We begin capitalization when the project is probable. The assets relating to the project are stated at cost and are not depreciated. Once construction is completed and the assets are placed in service, the assets are reclassified to the appropriate asset class and depreciated in accordance with the useful lives as indicated below. Capitalization of interest ceases when the asset is ready for its intended use, which is generally near the date that a certificate of occupancy is obtained. Total capitalized interest for the year ended December 31, 2017 was $0.5 million . There was no capitalized interest for the years ended December 31, 2016 and 2015. Depreciation and amortization are computed using the straight-line method for financial reporting purposes. Buildings and improvements are depreciated over the shorter of 39 years, the useful life, or the remaining term of any leasehold interest. Tenant improvement costs, which are included in building and improvements in the consolidated balance sheets, are depreciated over the shorter of (i) the related remaining lease term or (ii) the life of the improvement. Corporate equipment, which is included in “Other assets,” is depreciated over three to seven years. Acquisitions of properties are accounted for utilizing the acquisition method and accordingly the purchase cost is allocated to tangible and intangible assets and liabilities based on their fair values. The fair value of tangible assets acquired is determined by valuing the property as if it were vacant, applying methods similar to those used by independent appraisers of income-producing property. The resulting value is then allocated to land, buildings and improvements, and tenant improvements based on our determination of the fair value of these assets. The assumptions used in the allocation of fair values to assets acquired are based on our best estimates at the time of evaluation. Fair value is assigned to above-market and below-market leases based on the difference between (a) the contractual amounts to be paid by the tenant based on the existing lease and (b) our estimate of current market lease rates for the corresponding in-place leases, over the remaining terms of the in-place leases. Capitalized above-market lease amounts are amortized as a decrease to rental revenue over the remaining terms of the respective leases. Capitalized below-market lease amounts are amortized as an increase to rental revenue over the remaining terms of the respective leases. If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The aggregate value of other acquired intangible assets consists of acquired ground leases and acquired in-place leases and tenant relationships. The fair value allocated to acquired in-place leases consists of a variety of components including, but not necessarily limited to: (a) the value associated with avoiding the cost of originating the acquired in-place leases (i.e. the market cost to execute a lease, including leasing commissions and legal fees, if any); (b) the value associated with lost revenue related to tenant reimbursable operating costs estimated to be incurred during the assumed lease-up period (i.e. real estate taxes, insurance and other operating expenses); (c) the value associated with lost rental revenue from existing leases during the assumed lease-up period; and (d) the value associated with any other inducements to secure a tenant lease. We assess the potential for impairment of our long-lived assets, including real estate properties, annually or whenever events occur or a change in circumstances indicate that the recorded value might not be fully recoverable. We determine whether impairment in value has occurred by comparing the estimated future undiscounted cash flows expected from the use and eventual disposition of the asset to its carrying value. If the undiscounted cash flows do not exceed the carrying value, the real estate is adjusted to fair value and an impairment loss is recognized. Assets held for sale are recorded at the lower of cost or fair value less costs to sell. We do not believe that the value of any of our properties and intangible assets were impaired during the years ended December 31, 2017, 2016 and 2015. Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, government money markets, demand deposits with financial institutions and short-term liquid investments with original maturities of three months or less when purchased. Cash and cash equivalents held at major commercial banks may at times exceed the Federal Deposit Insurance Corporation limit. To date, we have not experienced any losses on our invested cash. Restricted Cash Restricted cash consists of amounts held for tenants in accordance with lease agreements such as security deposits and amounts held by lenders and/or escrow agents to provide for future real estate tax expenditures and insurance expenditures, tenant vacancy related costs and debt service obligations. Tenant and Other Receivables Tenant and other receivables, other than deferred rent receivable, are generally expected to be collected within one year. Allowance for Doubtful Accounts We maintain an allowance against tenant and other receivables and deferred rents receivables for future potential tenant credit losses. The credit assessment is based on the estimated accrued rental revenue that is recoverable over the term of the respective lease. The computation of this allowance is based on the tenants’ payment history and current credit status. If our estimate of collectability differs from the cash received, then the timing and amount of our reported revenue could be impacted. Bad debt expense is included in operating expenses on our consolidated statements of income and includes the impact of changes in the allowance for doubtful accounts on our consolidated balance sheets. Deferred Leasing Costs Deferred leasing costs consist of fees and direct costs incurred to initiate and renew leases, are amortized on a straight-line basis over the related lease term and the expense is included in depreciation and amortization in our consolidated statements of income. Upon the early termination of a lease, unamortized deferred leasing costs are charged to expense. Deferred Financing Costs Fees and costs incurred to obtain long-term financing have been deferred and are amortized as a component of interest expense in our consolidated statements of income over the life of the respective long-term financing on the straight-line method which approximates the effective interest method. Unamortized deferred financing costs are expensed when the associated debt is refinanced or repaid before maturity. Costs incurred in seeking debt, which do not close, are expensed in the period in which it is determined that the financing will not close. Equity Method Investments We account for investments under the equity method of accounting where we do not have control but have the ability to exercise significant influence. Under this method, investments are recorded at cost, and the investment accounts are adjusted for our share of the entities’ income or loss and for distributions and contributions. Equity income (loss) is allocated based on the portion of the ownership interest that is controlled by us. The agreements may designate different percentage allocations among investors for profits and losses; however, our recognition of the entity’s income or loss generally follows the entity’s distribution priorities, which may change upon the achievement of certain investment return thresholds. To the extent that we contributed assets to an entity, our investment in the entity is recorded at cost basis in the assets that were contributed to the entity. Upon contributing assets to an entity, we make a judgment as to whether the economic substance of the transaction is a sale. If so, gain or loss is recognized on the portion of the asset to which the other partners in the entity obtain an interest. To the extent that the carrying amount of these investments on our combined balance sheets is different than the basis reflected at the entity level, the basis difference would be amortized over the life of the related asset and included in our share of equity in net income of the entity. On a periodic basis, we assess whether there are any indicators that the carrying value of our investments in entities may be impaired on an other than temporary basis. An investment is impaired only if management’s estimate of the fair value of the investment is less than the carrying value of the investment on an other than temporary basis. To the extent impairment has occurred, the loss shall be measured as the excess of the carrying value of the investment over the fair value of the investment. As of December 31, 2017 and 2016, we had no equity method investments. Goodwill Goodwill is tested annually for impairment and is tested for impairment more frequently if events and circumstances indicate that the asset might be impaired. An impairment loss is recognized to the extent that the carrying amount, including goodwill, exceeds the reporting unit’s fair value and the implied fair value of goodwill is less than the carrying amount of that goodwill. Non-amortizing intangible assets, such as trade names and trademarks, are subject to an annual impairment test based on fair value and amortizing intangible assets are tested whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Fair Value Fair value is a market-based measurement, not an entity-specific measurement, and should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, the Financial Accounting Standards Board ("FASB") guidance establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within levels one and two of the hierarchy) and the reporting entity's own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the hierarchy). The methodologies used for valuing financial instruments have been categorized into three broad levels as follows: Level 1 - Quoted prices in active markets for identical instruments. Level 2 - Valuations based principally on other observable market parameters, including: • Quoted prices in active markets for similar instruments; • Quoted prices in less active or inactive markets for identical or similar instruments; • Other observable inputs (such as risk free interest rates, yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates); and • Market corroborated inputs (derived principally from or corroborated by observable market data). Level 3 - Valuations based significantly on unobservable inputs, including: • Valuations based on third-party indications (broker quotes or counterparty quotes) which were, in turn, based significantly on unobservable inputs or were otherwise not supportable; and • Valuations based on internal models with significant unobservable inputs. These levels form a hierarchy. We follow this hierarchy for our financial instruments measured or disclosed at fair value on a recurring and nonrecurring basis and other required fair value disclosures. The classifications are based on the lowest level of input that is significant to the fair value measurement. We use the following methods and assumptions in estimating fair value disclosures for financial instruments. Cash and cash equivalents, restricted cash, tenant and other receivables, prepaid expenses and other assets, deferred revenue, tenant security deposits, accounts payable and accrued expenses carrying values approximate their fair values due to the short term maturity of these instruments. The fair value of our senior unsecured notes - exchangeable was derived from quoted prices in active markets and is classified as Level 2 since trading volumes are low. The fair value of derivative instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Although the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by ourselves and our counterparties. The impact of such credit valuation adjustments, determined based on the fair value of each individual contract, was not significant to the overall valuation. As a result, all of our derivatives were classified as Level 2 of the fair value hierarchy. The fair value of our mortgage notes payable, unsecured revolving credit and term loan facility, and senior unsecured notes - Series A, B, C and D which are determined using Level 3 inputs, are estimated by discounting the future cash flows using current interest rates at which similar borrowings could be made to us. Derivative Instruments We are exposed to the effect of interest rate changes and manage these risks by following policies and procedures including the use of derivatives. To manage exposure to interest rates, derivatives are used primarily to fix the rate on debt based on floating-rate indices. We also hedge exposure to the variability in future cash flows for forecast transactions over a maximum period of 11 months (excluding forecast transactions related to the payment of variable interest on existing financial instruments). We record all derivatives on the balance sheet at fair value. We incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. We measure the credit risk of our derivative instruments that are subject to master netting agreements on a net basis by counterparty portfolio. For derivatives that qualify as cash flow hedges, we report the gain or loss on the derivative designated as a hedge as part of other comprehensive income (loss) and subsequently reclassify the gain or loss into income in the period that the hedged transaction affects income. Income Taxes We elected to be taxed as a REIT under sections 856 through 860 of the Internal Revenue Code of 1986, as amended, (the "Code"), commencing with the taxable year ended December 31, 2013 and believe we qualify as a REIT at December 31, 2017. REITs are subject to a number of organizational and operational requirements, including a requirement that 90% of ordinary “REIT taxable income” (as determined without regard to the dividends paid deduction or net capital gains) be distributed. As a REIT, we will generally not be subject to U.S. federal income tax to the extent that we meet the organizational and operational requirements and our distributions equal or exceed REIT taxable income. For all periods subsequent to the effective date of our REIT election, we have met the organizational and operational requirements and distributions have exceeded net taxable income. Accordingly, no provision has been made for federal and state income taxes. We have elected to treat ESRT Observatory TRS, L.L.C., our subsidiary which holds our observatory operations, and ESRT Holdings TRS, L.L.C., our subsidiary that holds our third party management, construction (through cessation of our construction business in the first quarter of 2015), restaurant, cafeteria, health clubs and certain cleaning operations, as taxable REIT subsidiaries. Taxable REIT subsidiaries may participate in non-real estate activities and/or perform non-customary services for tenants and their operations are generally subject to regular corporate income taxes. Our taxable REIT subsidiaries accounts for its income taxes in accordance with GAAP, which includes an estimate of the amount of taxes payable or refundable for the current year and deferred tax liabilities and assets for the future tax consequences of events that have been recognized in our financial statements or tax returns. The calculation of the taxable REIT subsidiaries' tax provisions may require interpreting tax laws and regulations and could result in the use of judgments or estimates which could cause its recorded tax liability to differ from the actual amount due. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The taxable REIT subsidiaries periodically assess the realizability of deferred tax assets and the adequacy of deferred tax liabilities, including the results of local, state, or federal statutory tax audits or estimates and judgments used. We apply provisions for measuring and recognizing tax benefits associated with uncertain income tax positions. Penalties and interest, if incurred, would be recorded as a component of income tax expense. As of December 31, 2017 and 2016, we do not have a liability for uncertain tax positions. As of December 31, 2017 , the tax years ended December 31, 2014 through December 31, 2017 remain open for an audit by the Internal Revenue Service, state or local authorities. Share-Based Compensation Share-based compensation is measured at the fair value of the award on the date of grant and recognized as an expense on a straight-line basis over the vesting period. The determination of fair value of these awards is subjective and involves significant estimates and assumptions including expected volatility of our stock, expected dividend yield, expected term, and assumptions of whether these awards will achieve parity with other operating partnership units or achieve performance thresholds. We believe that the assumptions and estimates utilized are appropriate based on the information available to management at the time of grant. Per Share Data Basic and diluted earnings per share are computed based upon the weighted average number of shares outstanding during the respective period. Segment Reporting We have identified two reportable segments: (1) Real Estate and (2) Observatory. Our real estate segment includes all activities related to the ownership, management, operation, acquisition, repositioning and disposition of our real estate assets. Our observatory segment operates the 86th and 102nd floor observatories at the Empire State Building. These two lines of businesses are managed separately because each business requires different support infrastructures, provides different services and has dissimilar economic characteristics such as investments needed, stream of revenues and different marketing strategies. We account for intersegment sales and rent as if the sales or rent were to third parties, that is, at current market prices. We include our construction operation in "Other" and it includes all activities related to providing construction services to tenants and to other entities within and outside our company. As of March 27, 2015, we no longer solicited new business for our construction management business. We completed all projects that were in progress. Reclassification Certain prior year balances have been reclassified to conform to our current year presentation. The 2016 and 2015 balance of interest expense relating to loss on early extinguishment of debt has been reclassified and presented separately on the consolidated statements of income. Recently Issued or Adopted Accounting Standards During August 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which amends its hedge accounting model to enable entities to better portray their risk management activities in the financial statements. The amendments expand an entity’s ability to hedge nonfinancial and financial risk components and reduce complexity in fair value hedges of interest rate risk. ASU No. 2017-12 eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. It also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU No. 2017-12 will be effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period. All transition requirements and elections should be applied to hedging relationships existing on the date of adoption. The effect of adoption should be reflected as of the beginning of the fiscal year of adoption (that is, the initial application date). During 2017, we early adopted ASU No. 2017-02 using a modified retrospective approach for existing and active hedging relationships as of adoption date. The adoption of ASU No. 2017-02 did not have a material impact on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which contain amendments that modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Because these amendments eliminate Step 2 from the goodwill impairment test, they should reduce the cost and complexity of evaluating goodwill for impairment. ASU No. 2017-04 should be applied on a prospective basis and the amendments adopted for the annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which contain amendments to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in ASU No. 2017-01 provide a screen to determine when an integrated set of assets and activities (collectively referred to as a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business.

Deferred Costs, Acquired Lease

Deferred Costs, Acquired Lease Intangibles and Goodwill	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Acquired Lease Intangibles and Goodwill	Deferred Costs, Acquired Lease Intangibles and Goodwill Deferred costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Leasing costs $ 164,751 $ 140,325 Acquired in-place lease value and deferred leasing costs 237,364 253,113 Acquired above-market leases 67,415 74,770 469,530 468,208 Less: accumulated amortization (215,102 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 254,428 $ 272,591 At December 31, 2017 and 2016, $8.3 million and $4.5 million , respectively, of net deferred financing costs associated with the unsecured revolving credit facility was included in deferred costs, net on the consolidated balance sheets. Amortization expense related to deferred leasing and acquired deferred leasing costs was $24.1 million , $24.2 million , and $25.4 million , for the years ended December 31, 2017 , 2016, and 2015, respectively. Amortization expense related to acquired lease intangibles was $17.1 million , $24.6 million and $37.7 million for the years ended December 31, 2017 , 2016 and 2015, respectively. Amortizing acquired intangible assets and liabilities consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (28,687 ) (20,856 ) Acquired below-market ground leases, net $ 368,229 $ 376,060 2017 2016 Acquired below-market leases $ (132,026 ) $ (135,026 ) Less: accumulated amortization 65,979 52,726 Acquired below-market leases, net $ (66,047 ) $ (82,300 ) Rental revenue related to the amortization of below market leases, net of above market leases was $5.7 million , $8.8 million and $19.4 million for the years ended December 31, 2017 , 2016 and 2015, respectively. The remaining weighted-average amortization period as of December 31, 2017 is 25.0 years, 4.8 years, 3.9 years and 4.2 years for below-market ground leases, in-place leases and deferred leasing costs, above-market leases and below-market leases, respectively. We expect to recognize amortization expense and rental revenue from the acquired intangible assets and liabilities as follows (amounts in thousands): For the year ending: Future Ground Rent Amortization Future Amortization Expense Future Rental Revenue 2018 $ 7,831 $ 18,650 $ 6,442 2019 7,831 15,996 6,689 2020 7,831 13,046 3,559 2021 7,831 11,302 2,857 2022 7,831 10,485 3,175 Thereafter 329,074 41,549 12,690 $ 368,229 $ 111,028 $ 35,412 As of December 31, 2017 , we had goodwill of $491.5 million . In 2013, we acquired the interests in Empire State Building Company, L.L.C. and 501 Seventh Avenue Associates, L.L.C. for an amount in excess of their net tangible and identified intangible assets and liabilities and as a result we recorded goodwill related to the transaction. Goodwill was allocated $227.5 million to the observatory operations of the Empire State Building, $250.8 million to Empire State Building, and $13.2 million to 501 Seventh Avenue. We performed an annual review of goodwill for impairment and concluded there was no impairment of goodwill. Our methodology to review goodwill impairment, which includes a significant amount of judgment and estimates, provides a reasonable basis to determine whether impairment has occurred. However, many of the factors employed in determining whether or not goodwill is impaired are outside of our control and it is reasonably likely that assumptions and estimates will change in future periods.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt Debt consisted of the following as of December 31, 2017 and 2016 (amounts in thousands): As of December 31, 2017 Principal Balance as Principal Balance as Stated Effective (1) Maturity (2) Fixed rate mortgage debt 1333 Broadway $ 66,602 $ 67,656 6.32 % 3.73 % 1/5/2018 1400 Broadway (first lien mortgage loan) 66,632 67,714 6.12 % 3.37 % 2/5/2018 (second lien mortgage loan) 9,172 9,389 3.35 % 3.36 % 2/5/2018 111 West 33rd Street (first lien mortgage loan) 74,045 75,261 6.01 % 3.34 % 4/5/2018 (second lien mortgage loan) 9,369 9,509 6.56 % 3.64 % 4/5/2018 1350 Broadway 37,144 37,764 5.87 % 3.71 % 4/5/2018 Metro Center 93,948 95,985 3.59 % 3.67 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 10 Bank Street 34,602 31,544 4.23 % 4.49 % 6/1/2032 1542 Third Avenue 30,000 17,795 4.29 % 4.64 % 5/1/2027 First Stamford Place (3) 180,000 235,067 4.28 % 4.60 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,710 26,502 4.01 % 4.39 % 1/5/2028 383 Main Avenue 30,000 28,654 4.44 % 4.72 % 6/30/2032 Total mortgage debt 721,224 752,840 Senior unsecured notes - exchangeable 250,000 250,000 2.63 % 3.93 % 8/15/2019 Senior unsecured notes: Series A 100,000 100,000 3.93 % 3.98 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.14 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.23 % 3/27/2030 Series D 115,000 — 4.08 % 4.08 % 1/22/2028 Series E (4) — — 4.26 % — % 3/22/2030 Series F (4) — — 4.44 % — % 3/22/2033 Unsecured revolving credit facility — — (5) (5) 8/29/2021 Unsecured term loan facility 265,000 265,000 (6) (6) 8/29/2022 Total principal 1,701,224 1,617,840 Unamortized (discount) premiums, net of unamortized premiums (discount) (3,370 ) 905 Deferred financing costs, net (9,133 ) (6,414 ) Total $ 1,688,721 $ 1,612,331 ______________ (1) The effective rate is the yield as of December 31, 2017, including the effects of debt issuance costs and the amortization of the fair value of debt adjustment. (2) Pre-payment is generally allowed for each loan upon payment of a customary pre-payment penalty. (3) Represents a $164 million mortgage loan bearing interest of 4.09% and a $16 million loan bearing interest at 6.25% . (4) Senior unsecured notes Series E, totaling $160 million , and Series F, totaling $175 million , will be issued during March 2018. (5) At December 31, 2017, the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at December 31, 2017 was 2.66% . (6) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to a forward interest rate swap agreement, the LIBOR rate is fixed at 2.1485% for the period beginning on August 31, 2017 through maturity. The rate at December 31, 2017 was 3.35% Mortgage Debt During April 2017, we refinanced a mortgage loan collateralized by 1542 Third Avenue. The new $30.0 million loan bears interest at a fixed rate of 4.29% and matures in May 2027. During May 2017, we refinanced a mortgage loan collateralized by 10 Bank Street. The new $35.0 million loan bears interest at a fixed rate of 4.23% and matures in June 2032. During June 2017, we refinanced a mortgage loan collateralized by First Stamford Place. The new $180.0 million loans bear a blended interest rate of 4.28% and mature in July 2027. One mortgage loan is for $164.0 million and bears an interest rate of 4.09% . The second loan is for $16.0 million and bears an interest rate of 6.25% . During June 2017, we refinanced a mortgage loan collateralized by 1010 Third Avenue and 77 West 55th Street. The new $40.0 million loan bears interest at a fixed rate of 4.01% and matures in January 2028. During June 2017, we refinanced a mortgage loan collateralized by 383 Main Avenue. The new $30.0 million loan bears interest at a fixed rate of 4.44% and matures in June 2032. During January 2018, we refinanced and increased our mortgage debt on 1333 Broadway from $66.6 million to $160.0 million , due February 2033 with interest fixed at 4.21% . A portion of this increase was applied to release the $75.8 million mortgage lien on 1400 Broadway. Principal Payments Aggregate required principal payments at December 31, 2017 are as follows (amounts in thousands): Year Amortization Maturities Total 2018 $ 4,417 $ 262,195 $ 266,612 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 2022 5,455 265,000 270,455 Thereafter 37,890 864,449 902,339 Total principal maturities $ 59,580 $ 1,641,644 $ 1,701,224 Deferred Financing Costs Deferred financing costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Financing costs $ 24,446 $ 23,145 Less: accumulated amortization (7,039 ) (12,241 ) Total deferred financing costs, net $ 17,407 $ 10,904 At December 31, 2017 and 2016, $8.3 million and $4.5 million , respectively, of net deferred financing costs associated with the unsecured revolving credit facility were included in deferred costs, net on the consolidated balance sheet. Amortization expense related to deferred financing costs was $4.7 million , $5.0 million , and $6.1 million , for the years ended December 31, 2017 , 2016, and 2015, respectively, and was included in interest expense. Unsecured Revolving Credit and Term Loan Facility During August 2017, through the Operating Partnership, we entered into an amended and restated senior unsecured revolving credit and term loan facility (the “Facility”) with Bank of America, N.A., as administrative agent, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Wells Fargo Securities, LLC as Joint Lead Arrangers and Joint Bookrunners, Wells Fargo, National Association and Capital One, National Association, as co-syndication agents, and the lenders party thereto. The Facility amended and restated the credit facility dated as of January 23, 2015, with Bank of America, N.A., Merrill Lynch, Goldman Sachs and the other lenders party thereto. In connection with the modification of the credit facility and term loan, we incurred a loss on early extinguishment of debt of $2.2 million which is reflected in our consolidated statement of income for the year ended December 31, 2017. This transaction extended the unsecured revolving credit and term loan facility maturity, lowered borrowing costs and added flexibility to the financial covenants. The Facility is in the original principal amount of up to $1.365 billion which consists of a $1.1 billion revolving credit facility and a $265.0 million term loan facility. The new revolving credit facility replaced a credit facility which was due to mature in January 2019 and was undrawn when amended. The term loan facility was borrowed in full at closing and used to repay a $265.0 million term loan that had been due in 2022. We may request the Facility be increased through one or more increases in the revolving credit facility or one or more increases in the term loan facility or the addition of new pari passu term loan tranches, for a maximum aggregate principal amount not to exceed $1.75 billion. The initial maturity of the unsecured revolving credit facility is August 2021. We have the option to extend the initial term for up to two additional 6 -month periods, subject to certain conditions, including the payment of an extension fee equal to 0.0625% and 0.075% of the then outstanding commitments under the unsecured revolving credit facility on the first and the second extensions, respectively. The term loan facility matures on August 2022. We may prepay the loans under the Facility at any time, subject to reimbursement of the lenders’ breakage and redeployment costs in the case of prepayment of Eurodollar Rate borrowings. The Facility includes the following financial covenants: (i) maximum leverage ratio of total indebtedness to total asset value (as defined in the agreement) of the loan parties and their consolidated subsidiaries will not exceed 60% , (ii) consolidated secured indebtedness will not exceed 40% of total asset value, (iii) tangible net worth will not be less than $1.2 billion plus 75% of net equity proceeds received by the Operating Partnership (other than proceeds received within ninety (90) days after the redemption, retirement or repurchase of ownership or equity interests in us up to the amount paid by us in connection with such redemption, retirement or repurchase, where, the net effect is that the Operating Partnership shall not have increased its net worth as a result of any such proceeds), (iv) adjusted EBITDA (as defined in the Facility) to consolidated fixed charges will not be less than 1.50 x, (v) the aggregate net operating income with respect to all unencumbered eligible properties to the portion of interest expense attributable to unsecured indebtedness will not be less than 1.75 x, and (vi) the ratio of total unsecured indebtedness to unencumbered asset value will not exceed 60% . The Facility contains customary covenants, including limitations on liens, investment, distributions, debt, fundamental changes, and transactions with affiliates, and requires certain customary financial reports. The Facility contains customary events of default (subject in certain cases to specified cure periods), including but not limited to non-payment, breach of covenants, representations or warranties, cross defaults, bankruptcy or other insolvency events, judgments, ERISA events, invalidity of loan documents, loss of real estate investment trust qualification, and occurrence of a change of control (defined in the agreement for the Facility). As of December 31, 2017 , we were in compliance with the covenants under the Facility. Senior Unsecured Notes Exchangeable During August 2014, we issued $250.0 million principal amount of 2.625% Exchangeable Senior Notes (“ 2.625% Exchangeable Senior Notes”) due August 15, 2019. Interest on the 2.625% Exchangeable Senior Notes is payable semi-annually in arrears on February 15 and August 15 of each year. The 2.625% Exchangeable Senior Notes are senior unsecured obligations and rank equally in right of payment with all of our other senior unsecured indebtedness and effectively subordinated in right of payment to all of our secured indebtedness (to the extent of the value of the collateral securing such indebtedness) and structurally subordinated to all liabilities and preferred equity of our subsidiaries. The 2.625% Exchangeable Senior Notes will mature on August 15, 2019, unless earlier exchanged, redeemed or repurchased. Holders may exchange their 2.625% Exchangeable Senior Notes at their option at any time prior to the close of business on the business day immediately preceding May 15, 2019 only under the following circumstances: (i) during any calendar quarter beginning after September 30, 2014 (and only during such quarter) if the closing sale price of our Class A common stock is more than 130% of the then current exchange price for at least 20 trading days (whether or not consecutive) in the period of the 30 consecutive trading days ending on the last trading day of the previous calendar quarter; (ii) during the five consecutive business-day period following any five consecutive trading-day period in which the trading price per 1,000 principal amount of the 2.625% Exchangeable Senior Notes for each trading day during such five consecutive trading-day period in which the trading price per 1,000 principal amount of the 2.625% Exchangeable Senior Notes for each trading day during such five trading-day period was less than 98% of the closing sale price of our Class A common stock, for each trading day during such five trading-day period multiplied by the then current exchange rate; (iii) if we call any or all of the 2.625% Exchangeable Senior Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date; or (iv) upon the occurrence of specified corporate transactions (significant consolidation, sale, merger, share exchange, fundamental change, etc.). On or after May 15, 2019, and on or prior to the second scheduled trading day immediately preceding the maturity date, holders may exchange their notes without regard to the foregoing conditions. The 2.625% Exchangeable Senior Notes will be exchangeable into cash, shares of Class A common stock or a combination of cash and shares of Class A common stock, at our election. We have asserted it is our intent and ability to settle the principal amount of the 2.625% Exchangeable Senior Notes in cash. The initial exchange rate of 2.625% Exchangeable Senior Notes is 51.4059 shares per $1,000 principal amount of notes (equivalent to an initial exchange price of approximately $19.45 per share of Class A common stock), subject to adjustment, as described in the related indenture governing the 2.625% Exchangeable Senior Notes. As of December 31, 2017 , the exchange rate of the 2.625% Exchangeable Senior Notes was 51.7605 shares per $1,000 principal amount of notes (equivalent to an initial exchange price of approximately $19.32 per share of Class A common stock), subject to adjustment, as described in the related indenture governing the 2.625% Exchangeable Senior Notes. Following certain corporate transactions which constitute a make-whole fundamental change (defined in the indenture), we will increase the exchange rate for holders who elect to exchange their 2.625% Exchangeable Senior Notes in connection with such make whole fundamental change in certain circumstances. Following certain corporate transactions which constitute a fundamental change, holders may require us to repurchase the 2.625% Exchangeable Senior Notes for cash at a price equal to 100% of the principal amount of the notes to be purchased plus any accrued and unpaid interest to, but excluding, the repurchase date. We have separately accounted for the liability and equity components of the 2.625% Exchangeable Senior Notes by bifurcating gross proceeds between the indebtedness, or liability component, and the embedded conversion option, or the equity component. The bifurcation was done by estimating an effective interest rate as of the date of the issuance for similar notes which do not contain an embedded conversion option. This effective interest rate was estimated to be 3.8% and was used to compute the fair value at the time of issuance for the indebtedness of $236.6 million . The gross proceeds from the issuance of the 2.625% Exchangeable Senior Notes less the initial amount allocated to the indebtedness resulted in a $13.4 million allocation to the embedded conversion option which is included in Equity, net of financing costs, in the consolidated balance sheets as of December 31, 2017 and 2016. The resulting debt discount is being amortized over the five year period in which the 2.625% Exchangeable Senior Notes are expected to be outstanding (that is, through maturity date) as additional non-cash interest expense. As of December 31, 2017 and 2016, the unamortized discount was $4.3 million and $7.0 million , respectively. Underwriting discounts and commissions and issuance costs totaled $3.1 million and were allocated to the indebtedness and the embedded conversion option on a pro-rata basis and accounted for as debt issuance costs and equity issuance costs, respectively. In this connection, $2.9 million attributable to the indebtedness was recorded as part of deferred costs, to be subsequently amortized using the effective interest method as interest expense over the expected term of the 2.625% Exchangeable Senior Notes, and $0.2 million attributable to the embedded conversion option was recorded as a reduction to Equity in the consolidated balance sheets as of December 31, 2017 and 2016. For the years ended December 31, 2017 , 2016 and 2015, total interest expense related to the 2.625% Exchangeable Senior Notes was $9.9 million , $9.9 million and $9.9 million , respectively, consisting of (i) contractual interest expense of $6.6 million , $6.6 million and $6.6 million , respectively, (ii) additional non-cash interest expense of $2.7 million , $2.7 million and $2.7 million , respectively, related to the accretion of the debt discount, and (iii) amortization of deferred financing costs of $0.6 million , $0.6 million and $0.6 million , respectively. Senior Unsecured Notes During December 2017, we entered into an agreement to issue and sell an aggregate principal amount of $450.0 million of senior unsecured notes consisting of $115.0 million of 4.08% Series D Senior Notes due 2028, $160.0 million of 4.26% Series E Senior Notes due 2030, and $175.0 million of 4.44% Series F Senior Notes due 2033. We issued and sold the Series D Senior Notes in December 2017. The issuance and sale of the Series E and F Senior Notes will occur in March 2018, subject to customary closing conditions. The terms of the Series A, B, C, D, E, and F senior notes agreements include customary covenants, including limitations on liens, investment, distributions, debt, fundamental changes, and transactions with affiliates and require certain customary financial reports. It also requires compliance with financial ratios including a maximum leverage ratio, a maximum secured leverage ratio, a minimum amount of tangible net worth, a minimum fixed charge coverage ratio, a minimum unencumbered interest coverage ratio, and a maximum unsecured leverage ratio. As of December 31, 2017 , we were in compliance with the covenants under the outstanding Senior Unsecured Notes.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following as of December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Accrued capital expenditures $ 71,769 $ 66,620 Accounts payable and accrued expenses 32,509 36,246 Payable to the estate of Leona M. Helmsley (1) — 18,367 Interest rate swap agreements liability 436 5,591 Accrued interest payable 5,687 6,230 Due to affiliated companies 448 1,010 Total accounts payable and accrued expenses $ 110,849 $ 134,064 ___________ (1) Reflects a payable to the estate of Leona M. Helmsley, as required under our formation agreements, for New York City transfer taxes which would have been payable in absence of the estate's exemption from such tax. The taxing authority's final approval of such exemption was issued during the three months ended September 30, 2017, and upon receipt of the confirming documents we made this payment to the estate of Leona M. Helmsley on October 2, 2017.

Financial Instruments and Fair

Financial Instruments and Fair Values	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Values	Financial Instruments and Fair Values Derivative Financial Instruments We use derivative financial instruments primarily to manage interest rate risk and such derivatives are not considered speculative. These derivative instruments are typically in the form of interest rate swap and forward agreements and the primary objective is to minimize interest rate risks associated with investing and financing activities. The counterparties of these arrangements are major financial institutions with which we may also have other financial relationships. We are exposed to credit risk in the event of non-performance by these counterparties; however, we currently do not anticipate that any of the counterparties will fail to meet their obligations. We have agreements with our derivative counterparties that contain a provision where if we either default or are capable of being declared in default on any of our indebtedness, then we could also be declared in default on our derivative obligations. As of December 31, 2017, the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $0.5 million . If we had breached any of these provisions at December 31, 2017, we could have been required to settle our obligations under the agreements at their termination value of $0.5 million . As of December 31, 2017 and 2016, we had interest rate LIBOR swaps with an aggregate notional value of $265.0 million and $890.0 million , respectively. The notional value does not represent exposure to credit, interest rate or market risks. As of December 31, 2017 , the fair value of this derivative instruments amounted to ( $0.4 million ) which is included in accounts payable and accrued expenses on the consolidated balance sheet. As of December 31, 2016, the fair value of these derivative instruments amounted to $0.6 million which is included in prepaid expenses and other assets and ( $5.6 million ) which is included in accounts payable and accrued expenses on the consolidated balance sheet. These interest rate swaps have been designated as cash flow hedges and hedge the future cash outflows on our mortgage debt and also on our term loan facility that is subject to a floating interest rate. As of December 31, 2017 and 2016, these cash flow hedges are deemed highly effective and a net unrealized loss of $10.5 million and $3.1 million , respectively, is reflected in the consolidated statements of comprehensive income (loss). Amounts reported in accumulated other comprehensive income (loss) related to derivatives will be reclassified to interest expense as interest payments are made on these debt. We estimate that $1.0 million of the current balance held in accumulated other comprehensive loss will be reclassified into interest expense within the next 12 months relating to the interest rate swap contract in effect as of December 31, 2017. The table below summarizes the terms of agreements and the fair values of our derivative financial instruments as of December 31, 2017 and 2016 (dollar amounts in thousands): December 31, 2017 December 31, 2016 Derivative Notional Amount Receive Rate Pay Rate Effective Date Expiration Date Asset Liability Asset Liability Interest rate swap $ 265,000 1 Month LIBOR 2.1485 % August 31, 2017 August 24, 2022 $ — $ (436 ) $ — $ (1,634 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.5050 % July 5, 2017 July 5, 2027 — — — (684 ) Interest rate swap (1) (2) 80,000 3 Month LIBOR 2.5050 % July 5, 2017 July 5, 2027 — — — (685 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 224 — Interest rate swap (1) 100,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 223 — Interest rate swap (1) 75,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 167 — Interest rate swap (1) 75,000 3 Month LIBOR 2.7620 % June 1, 2018 June 1, 2028 — — — (1,295 ) Interest rate swap (1) 75,000 3 Month LIBOR 2.7620 % June 1, 2018 June 1, 2028 — — — (1,293 ) $ — $ (436 ) $ 614 $ (5,591 ) (1) During 2017, these swaps were terminated in connection with the refinancing of several of our mortgage debt (see Note 4 Debt). As of December 31, 2017, the deferred net losses from these terminated hedges amounted to $15.1 million which is included in accumulated other comprehensive loss relating to net unrealized loss from derivative financial instruments. We will reclassify into earnings, as an increase to interest expense, approximately $1.5 million per year over the 10 -year terms of the related debt due 2027, from the balance that is included in accumulated other comprehensive income on the consolidated balance sheets. (2) During March 2017, $20.0 million of an original notional amount of $100.0 million was terminated. In connection with the partial termination and re-designation of the related cash flow hedges, $0.3 million is recognized as a loss from derivative financial instruments and included in Other Expenses on the consolidated statement of income for the year ended December 31, 2017. There were no losses from derivative financial instruments for the years ended December 31, 2016 and 2015. The table below shows the effect of our derivative financial instruments designated as cash flow hedges on accumulated other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015 (amounts in thousands): Effects of Cash Flow Hedges December 31, 2017 December 31, 2016 December 31, 2015 Amount of gain (loss) recognized in other comprehensive income (loss) $ (11,658 ) $ (3,054 ) $ (1,922 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (1,142 ) — — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the consolidated statements of income for the years ended December 31, 2017, 2016 and 2015 (amounts in thousands): Effects of Cash Flow Hedges December 31, 2017 December 31, 2016 December 31, 2015 Total interest (expense) presented on the consolidated statements of income in which the effects of cash flow hedges are recorded $ (68,473 ) $ (70,595 ) $ (65,743 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (1,142 ) — — Fair Valuation The estimated fair values at December 31, 2017 and 2016 were determined by management, using available market information and appropriate valuation methodologies. Considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the estimates presented herein are not necessarily indicative of the amounts we could realize on disposition of the financial instruments. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The following tables summarize the carrying and estimated fair values of our financial instruments as of December 31, 2017 and 2016 (amounts in thousands): December 31, 2017 Carrying Value Estimated Fair Value Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ — $ — $ — $ — $ — Interest rate swaps included in accounts payable and accrued expenses 436 436 — 436 — Mortgage notes payable 717,164 707,300 — — 707,300 Senior unsecured notes - Exchangeable 244,739 275,723 — 275,723 — Senior unsecured notes - Series A, B, C, D, E and F 463,156 460,352 — — 460,352 Unsecured term loan facility 263,662 265,000 — — 265,000 December 31, 2016 Carrying Value Estimated Fair Value Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 614 $ 614 $ — $ 614 $ — Interest rate swaps included in accounts payable and accrued expenses 5,591 5,591 — 5,591 — Mortgage notes payable 759,016 755,640 — — 755,640 Senior unsecured notes - Exchangeable 241,474 282,435 — 282,435 — Senior unsecured notes - Series A, B, and C 348,914 339,274 — — 339,274 Unsecured term loan facility 262,927 265,000 — — 265,000 Disclosure about the fair value of financial instruments is based on pertinent information available to us as of December 31, 2017 and 2016 . Although we are not aware of any factors that would significantly affect the reasonable fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein.

Rental Income

Rental Income	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Rental Income	Rental Income We lease various spaces to tenants over terms ranging from one to 21 years. Certain leases have renewal options for additional terms. The leases provide for base monthly rentals and reimbursements for real estate taxes, escalations linked to the consumer price index or common area maintenance known as operating expense escalation. Operating expense reimbursements are reflected in our consolidated statements of income as tenant expense reimbursement. As of December 31, 2017 , we were entitled to the following future contractual minimum lease payments on non-cancellable operating leases to be received which expire on various dates through 2038 (amounts in thousands): 2018 $ 463,110 2019 451,161 2020 413,745 2021 381,394 2022 351,431 Thereafter 1,649,567 $ 3,710,408 The above future minimum lease payments exclude tenant recoveries, amortization of deferred rent receivables and the net accretion of above-below-market lease intangibles. Some leases are subject to termination options generally upon payment of a termination fee. The preceding table is prepared assuming such options are not exercised.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings Litigation Except as described below, as of December 31, 2017 , we were not involved in any material litigation, nor, to our knowledge, was any material litigation threatened against us or our properties, other than routine litigation arising in the ordinary course of business such as disputes with tenants. We believe that the costs and related liabilities, if any, which may result from such actions will not materially affect our condensed consolidated financial position, operating results or liquidity. As previously disclosed, in October 2014, 12 former investors in Empire State Building Associates L.L.C. (“ESBA”), which prior to the initial public offering of our company (the "Offering"), owned the fee title to the Empire State Building, filed an arbitration with the American Arbitration Association against Peter L. Malkin, Anthony E. Malkin, Thomas N. Keltner, Jr., and our subsidiary ESRT MH Holdings LLC, the former supervisor of ESBA, as respondents. The statement of claim (also filed later in federal court in New York for the expressed purpose of tolling the statute of limitations) alleges breach of fiduciary duty and related claims in connection with the Offering and formation transactions and seeks monetary damages and declaratory relief. These investors had opted out of a prior class action bringing similar claims that was settled with court approval. The respondents filed an answer and counterclaims. In March 2015, the federal court action was stayed on consent of all parties pending the arbitration. Arbitration hearings for a select number of sessions started in May 2016 and are now scheduled through July 2018. The respondents believe the allegations in the arbitration are entirely without merit, and they intend to continue to defend them vigorously. Pursuant to indemnification agreements which were made with our directors, executive officers and chairman emeritus as part of our formation transactions, Anthony E. Malkin, Peter L. Malkin and Thomas N. Keltner, Jr. have defense and indemnity rights from us with respect to this arbitration. Ground Lease Commitments We make payments under ground leases related to three of our properties. Minimum rent is expensed on a straight-line basis over the non-cancellable term of the leases. The ground leases are due to expire between the years 2050 and 2077. Future minimum lease payments to be paid over the terms of the leases are as follows (amounts in thousands): 2018 $ 1,518 2019 1,518 2020 1,518 2021 1,518 2022 1,518 Thereafter 53,694 Total $ 61,284 Unfunded Capital Expenditures At December 31, 2017 , we estimate that we will incur approximately $78.2 million of capital expenditures (including tenant improvements and leasing commissions) on our properties pursuant to existing lease agreements. We expect to fund these capital expenditures with operating cash flow, additional property level mortgage financings, our unsecured credit facility, cash on hand and other borrowings. Future property acquisitions may require substantial capital investments for refurbishment and leasing costs. We expect that these financing requirements will be met in a similar fashion. Concentration of Credit Risk Financial instruments that subject us to credit risk consist primarily of cash and cash equivalents, restricted cash, tenant and other receivables and deferred rent receivables. At December 31, 2017 , we held on deposit at various major financial institutions cash and cash equivalents and restricted cash balances in excess of amounts insured by the Federal Deposit Insurance Corporation. Real Estate Investments Our properties are located in Manhattan, New York; Fairfield County, Connecticut; and Westchester County, New York. The latter locations are suburbs of the city of New York. The ability of the tenants to honor the terms of their respective leases is dependent upon the economic, regulatory and social factors affecting the markets in which the tenants operate. We perform ongoing credit evaluations of our tenants for potential credit losses. Tenant Credit Evaluations Our investments in real estate properties are subject to risks incidental to the ownership and operation of commercial real estate. These risks include, among others, the risks normally associated with changes in general economic conditions, trends in the real estate industry, creditworthiness of tenants, competition of tenants and customers, changes in tax laws, interest rate levels, the availability and cost of financing, and potential liability under environmental and other laws. We may require tenants to provide some form of credit support such as corporate guarantees and/or other financial guarantees and we perform ongoing credit evaluations of tenants. Although the tenants operate in a variety of industries, to the extent we have a significant concentration of rental revenue from any single tenant, the inability of that tenant to make its lease payments could have an adverse effect on our company. Major Customers and Other Concentrations For the year ended December 31, 2017, other than five tenants who accounted for 6.3% , 3.2% , 2.9% , 2.1% and 2.0% of rental revenues, no other tenant in our portfolio accounted for more than 2.0% of rental revenues. For the year ended December 31, 2016, other than five tenants who accounted for 6.4% , 3.3% , 2.9% , 2.3% and 2.0% of rental revenues, no other tenant in our portfolio accounted for more than 2.0% of rental revenues. For the year ended December 31, 2015, other than three tenants who accounted for 6.7% , 3.5% and 2.0% of rental revenues, no other tenant in our portfolio accounted for more than 2.0% of rental revenues. For the years ended December 31, 2017 , 2016 and 2015, the six properties listed below accounted for the indicated percentage of total rental revenues. No other property accounted for more than 5.0% of total rental revenues. Year Ended December 31, 2017 2016 2015 Empire State Building 32.0 % 32.6 % 31.4 % One Grand Central Place 13.1 % 12.5 % 12.2 % 111 West 33rd Street 8.6 % 6.8 % 8.3 % 1400 Broadway 7.4 % 7.8 % 7.7 % First Stamford Place 5.4 % 6.4 % 6.5 % 250 West 57th Street 5.2 % 5.3 % 4.8 % Asset Retirement Obligations We are required to accrue costs that we are legally obligated to incur on retirement of our properties which result from acquisition, construction, development and/or normal operation of such properties. Retirement includes sale, abandonment or disposal of a property. Under that standard, a conditional asset retirement obligation represents a legal obligation to perform an asset retirement activity in which the timing and/or method of settlement is conditional on a future event that may or may not be within a company’s control and a liability for a conditional asset retirement obligation must be recorded if the fair value of the obligation can be reasonably estimated. Environmental site assessments and investigations have identified asbestos or asbestos-containing building materials in certain of our properties. As of December 31, 2017 , management has no plans to remove or alter these properties in a manner that would trigger federal and other applicable regulations for asbestos removal, and accordingly, the obligations to remove the asbestos or asbestos-containing building materials from these properties have indeterminable settlement dates. As such, we are unable to reasonably estimate the fair value of the associated conditional asset retirement obligation. However ongoing asbestos abatement, maintenance programs and other required documentation are carried out as required and related costs are expensed as incurred. Other Environmental Matters Certain of our properties have been inspected for soil contamination due to pollutants, which may have occurred prior to our ownership of these properties or subsequently in connection with its development and/or its use. Required remediation to such properties has been completed and, as of December 31, 2017 , management believes that there are no obligations related to environmental remediation other than maintaining the affected sites in conformity with the relevant authority’s mandates and filing the required documents. All such maintenance costs are expensed as incurred. We expect that resolution of the environmental matters relating to the above will not have a material impact on our business, assets, consolidated and combined financial condition, results of operations or liquidity. However, we cannot be certain that we have identified all environmental liabilities at our properties, that all necessary remediation actions have been or will be undertaken at our properties or that we will be indemnified, in full or at all, in the event that such environmental liabilities arise. Insurance Coverage We carry insurance coverage on our properties of types and in amounts with deductibles that we believe are in line with coverage customarily obtained by owners of similar properties. Multiemployer Pension and Defined Contribution Plans We contribute to a number of multiemployer defined benefit pension plans under the terms of collective bargaining agreements that cover our union-represented employees. The risks of participating in these multiemployer plans are different from single-employer plans in the following respects: • Assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers. • If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers. • If we choose to stop participating in some of our multiemployer plans, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability. We participate in various unions. The union in which we have significant employees and costs is 32BJ. 32BJ We participate in the Building Service 32BJ, ("Union"), Pension Plan and Health Plan. The Pension Plan is a multi-employer, non-contributory defined benefit pension plan that was established under the terms of collective bargaining agreements between the Service Employees International Union, Local 32BJ, the Realty Advisory Board on Labor Relations, Inc. and certain other employers. This Pension Plan is administered by a joint board of trustees consisting of union trustees and employer trustees and operates under employer identification number 13-1879376. The Pension Plan year runs from July 1 to June 30. Employers contribute to the Pension Plan at a fixed rate on behalf of each covered employee. Separate actuarial information regarding such pension plans is not made available to the contributing employers by the union administrators or trustees, since the plans do not maintain separate records for each reporting unit. However, on September 28, 2015, September 28, 2016 and September 28, 2017, the actuary certified that for the plan years beginning July 1, 2015, July 1, 2016 and July 1, 2017, respectively, the Pension Plan was in critical status under the Pension Protection Act of 2006. The Pension Plan trustees adopted a rehabilitation plan consistent with this requirement. For each of the years ended June 30, 2017, 2016 and 2015, the Pension Plan received contributions from employers totaling $257.8 million , $249.5 million and $242.3 million , respectively. The Health Plan was established under the terms of collective bargaining agreements between the Union, the Realty Advisory Board on Labor Relations, Inc. and certain other employers. The Health Plan provides health and other benefits to eligible participants employed in the building service industry who are covered under collective bargaining agreements, or other written agreements, with the Union. The Health Plan is administered by a Board of Trustees with equal representation by the employers and the Union and operates under employer identification number 13-2928869. The Health Plan receives contributions in accordance with collective bargaining agreements or participation agreements. Generally, these agreements provide that the employers contribute to the Health Plan at a fixed rate on behalf of each covered employee. For the years ended June 30, 2017, 2016 and 2015, the Health Plan received contributions from employers totaling $1.3 billion , $1.2 billion and $1.1 billion , respectively. Term of Collective Bargaining Agreement The most recent collective bargaining agreement for Local 32BJ commenced from January 1, 2016 and runs through December 31, 2019. Contributions Contributions we made to the multi-employer plans for the years ended December 31, 2017, 2016 and 2015 are included in the table below (amounts in thousands): For the Year Ended December 31, Benefit Plan 2017 2016 2015 Pension Plans (pension and annuity)* $ 3,035 $ 3,155 $ 3,077 Health Plans** 8,551 8,280 8,296 Other*** 856 542 619 Total plan contributions $ 12,442 $ 11,977 $ 11,992 * Pension plans include $0.9 million, $0.8 million and $0.7 million for the years ended 2017, 2016 and 2015, respectively, to multiemployer plans not discussed above. ** Health plans include $1.6 million, $1.6 million and $1.4 million for the years ended 2017, 2016 and 2015, respectively, to multiemployer plans not discussed above. *** Other consists of union costs which were not itemized between pension and health plans. Other includes $0.2 million, $0.2 million and $0.2 million for the years ended 2017, 2016 and 2015, respectively, in connection with other multiemployer plans not discussed above. Benefit plan contributions are included in property operating expenses in our consolidated statements of income.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note Disclosure, Disclosure of Compensation Related Costs, Share-based Payments and Earnings Per Share [Abstract]
Equity	Equity During 2016, Q REIT Holding LLC, a Qatar Financial Centre limited liability company and a wholly owned subsidiary of the Qatar Investment Authority, a governmental authority of the State of Qatar ("QREIT", and together with any eligible transferee, "QIA"), purchased 29,610,854 newly issued Class A common shares at $21.00 per share, equivalent to a 9.9% economic interest in us on a fully diluted basis (representing a 19.4% ownership of Class A common shares). However, QIA can only vote shares equivalent to 9.9% of all voting securities, with the balance of their shares to be voted by us in accord with the votes of all other voting securities. We received approximately $621.8 million in gross proceeds from the sale. QIA has a top-up right to acquire a pro rata number of additional shares from us in the future should we issue new shares to third parties. Shares and Units An operating partnership unit ("OP Unit") and a share of our common stock have essentially the same economic characteristics as they receive the same per unit profit distributions of our operating partnership. On the one-year anniversary of issuance, an OP Unit may be tendered for redemption for cash, however, we have sole and absolute discretion and the authorized common stock to exchange for shares of common stock on a one-for-one basis instead of cash. Long-term incentive plan ("LTIP") units are a special class of partnership interests in our operating partnership. Each LTIP unit awarded will be deemed equivalent to an award of one share of stock under the Empire State Realty Trust Inc. Empire State Realty OP, L.P. 2013 Equity Incentive Plan ("2013 Plan"), reducing the availability for other equity awards on a one-for-one basis. The vesting period for LTIP units, if any, will be determined at the time of issuance. Under the terms of the LTIP units, our operating partnership will revalue for tax purposes its assets upon the occurrence of certain specified events, and any increase in valuation from the time of grant until such event will be allocated first to the holders of LTIP units to equalize the capital accounts of such holders with the capital accounts of OP unitholders. Subject to any agreed upon exceptions, once vested and having achieved parity with OP unitholders, LTIP units are convertible into OP Units in our operating partnership on a one-for-one basis. With the exception of performance based LTIP units granted in 2016 and 2017, all LTIP units issued in connection with annual equity awards, whether vested or not, receive the same per unit distributions as operating partnership units, which equal per share dividends (both regular and special) on our common stock. Performance based LTIP units granted in 2016 and 2017 receive 10% of such distributions currently, unless and until such LTIP units are earned based on performance, at which time they will receive the accrued and unpaid 90% and will commence receiving 100% of such distributions thereafter. The following is net income attributable to common stockholders and the issuance of our class A shares in exchange for the conversion of OP units into common stock (amounts in thousands): Year ended December 31, 2017 2016 2015 Net income attributable to common stockholders $ 62,647 $ 51,456 $ 33,730 Increase in additional paid-in capital for the conversion of OP units into common stock 23,529 24,044 62,003 Change from net income attributable to common stockholders and transfers from noncontrolling interests $ 86,176 $ 75,500 $ 95,733 As of December 31, 2017 , there were approximately 300.4 million OP Units outstanding, of which approximately 161.5 million , or 53.8% , were owned by us and approximately 138.9 million , or 46.2% , were owned by other partners, including certain directors, officers and other members of executive management. Private Perpetual Preferred Units As of December 31, 2017 , there were 1,560,360 Private Perpetual Preferred Units ("Preferred Units") which have a liquidation preference of $16.62 per unit and which are entitled to receive cumulative preferential annual cash distributions of $0.60 per unit payable in arrears on a quarterly basis. The Preferred Units are not redeemable at the option of the holders and are redeemable at our option only in the case of specific defined events. Dividends and Distributions The following table summarizes the dividends paid on our Class A common stock and Class B common stock for the years ended December 31, 2017, 2016 and 2015: Record Date Payment Date Amount per Share December 15, 2017 December 29, 2017 $0.105 September 15, 2017 September 29, 2017 $0.105 June 15, 2017 June 30, 2017 $0.105 March 15, 2017 March 31, 2017 $0.105 December 15, 2016 December 29, 2016 $0.105 September 19, 2016 September 30, 2016 $0.105 June 15, 2016 June 30, 2016 $0.105 March 16, 2016 March 31, 2016 $0.085 December 15, 2015 December 31, 2015 $0.085 September 15, 2015 September 30, 2015 $0.085 June 15, 2015 June 30, 2015 $0.085 March 13, 2015 March 31, 2015 $0.085 Total dividends paid to common securityholders during 2017, 2016 and 2015 were $66.8 million , $55.8 million and $39.2 million , respectively. Total distributions paid to OP unitholders, excluding inter-company distributions, during 2017, 2016 and 2015 totaled $59.2 million , $58.2 million and $51.8 million , respectively. Total distributions paid to Preferred unitholders during 2017, 2016 and 2015 were $0.9 million , $0.9 million and $0.9 million , respectively. Earnings and profits, which determine the tax treatment of distributions to securityholders, will differ from income reported for financial reporting purposes due to the differences for federal income tax purposes, including, but not limited to, treatment of loss on extinguishment of debt, revenue recognition, compensation expense, and basis of depreciable assets and estimated useful lives used to compute depreciation. The 2017, 2016 and 2015 dividends of $0.42 , $0.40 and $0.34 per share, respectively, are classified for income tax purposes as 100.0% taxable ordinary dividends. Incentive and Share-Based Compensation The 2013 Plan provides for grants to our directors, employees and consultants consisting of stock options, restricted stock, dividend equivalents, stock payments, performance shares, LTIP units, stock appreciation rights and other incentive awards. An aggregate of approximately 12.2 million shares of our common stock are authorized for issuance under awards granted pursuant to the 2013 Plan, and as of December 31, 2017 , approximately 7.0 million shares of common stock remain available for future issuance. In May 2017, we made grants of LTIP units to our non-employee directors under the 2013 Plan. At such time, we granted a total of 50,408 LTIP units that are subject to time-based vesting with fair market values of $1.0 million . The awards vest ratably over three years from the date of the grant, subject generally to the director's continued service on our Board of Directors. In March 2017, we made grants of LTIP units to executive officers under the 2013 Plan. At such time, we granted to executive officers a total of 313,275 LTIP units that are subject to time-based vesting and 865,742 LTIP units that are subject to performance-based vesting, with fair market values of $6.1 million for the time-based vesting awards and $9.6 million for the performance-based vesting awards. In March 2017, we made grants of LTIP units and restricted stock to certain other employees under the 2013 Plan. At such time, we granted to certain other employees a total of 47,993 LTIP units and 34,407 shares of restricted stock that are subject to time-based vesting and 95,156 LTIP units that are subject to performance-based vesting, with fair market values of $1.6 million for the time-based vesting awards and $1.0 million for the performance-based vesting awards. The awards subject to time-based vesting vest ratably over four years from January 1, 2017, subject generally to the grantee's continued employment. The first installment vests on January 1, 2018 and the remainder will vest thereafter in three equal annual installments. The vesting of the LTIP units subject to performance-based vesting is based on the achievement of absolute and relative total stockholder return hurdles over a three -year performance period, commencing on January 1, 2017. Following the completion of the three -year performance period, our compensation committee will determine the number of LTIP units to which the grantee is entitled based on our performance relative to the performance hurdles set forth in the LTIP unit award agreements the grantee entered into in connection with the award grant. These units then vest in two installments, with the first installment vesting on January 1, 2020 and the second installment vesting on January 1, 2021, subject generally to the grantee's continued employment on those dates. In June 2016, we made grants of LTIP units to our non-employee directors under the 2013 Plan. At such time, we granted a total of 43,257 LTIP units that are subject to time-based vesting with fair market values of $0.8 million . The awards vest ratably over three years from the date of the grant, subject generally to the director's continued service on our Board of Directors. In February 2016, we made grants of LTIP units to executive officers under the 2013 Plan. At such time, we granted a total of 368,225 LTIP units that are subject to time-based vesting and 1,230,228 LTIP units that are subject to performance-based vesting, with fair market values of $5.6 million for the time-based vesting awards and $8.8 million for the performance-based vesting awards. In February 2016, we made grants of LTIP units and restricted stock to certain other employees under the 2013 Plan. At such time, we granted a total of 47,168 LTIP units and 44,198 shares of restricted stock that are subject to time-based vesting and 112,925 LTIP units that are subject to performance-based vesting, with fair market values of $1.4 million for the time-based vesting awards and $0.8 million for the performance-based vesting awards. The awards subject to time-based vesting vest ratably over four years from January 1, 2016, subject generally to the grantee's continued employment. The first installment vests on January 1, 2017 and the remainder will vest thereafter in three equal annual installments. The vesting of the LTIP units subject to performance-based vesting is based on the achievement of absolute and relative total stockholder return hurdles over a three -year performance period, commencing on January 1, 2016. Following the completion of the three -year performance period, our compensation committee will determine the number of LTIP units to which the grantee is entitled based on our performance relative to the performance hurdles set forth in the LTIP unit award agreements the grantee entered into in connection with the award grant. These units then vest in two installments, with the first installment vesting on January 1, 2019 and the second installment vesting on January 1, 2020, subject generally to the grantee's continued employment on those dates. In February 2016, we made a grant of LTIP units to an executive officer under the 2013 Plan. We granted a total of 62,814 LTIP units with a fair market value of $1.0 million . The award is subject to time-based vesting of 30% after three years, 30% after four years, and 40% after five years, subject to the grantee's continued employment. We made other grants during 2016 with fair market values of $0.1 million in the aggregate. Share-based compensation is measured at the fair value of the award on the date of grant and recognized as an expense on a straight-line basis over the vesting period. For the performance-based LTIP units and restricted stock awards, the fair value of the awards was estimated using a Monte Carlo Simulation model. Our stock price, along with the prices of the comparative indexes, is assumed to follow the Geometric Brownian Motion Process. Geometric Brownian motion is a common assumption when modeling in financial markets, as it allows the modeled quantity (in this case, the stock price) to vary randomly from its current value and take any value greater than zero . The volatilities of the returns on our stock price and the comparative indexes were estimated based on implied volatilities and historical volatilities using a six -year look-back period. The expected growth rate of the stock prices over the performance period is determined with consideration of the risk free rate as of the grant date. For LTIP unit awards that are time-based, the fair value of the awards was estimated based on the fair value of our stock at the grant date discounted for the restriction period during which the LTIP units cannot be redeemed or transferred and the uncertainty regarding if, and when, the book capital account of the LTIP units will equal that of the common units. For restricted stock awards that are time-based, we estimate the stock compensation expense based on the fair value of the stock at the grant date. LTIP units and restricted stock issued during the year ended December 31, 2017, 2016 and 2015 were valued at $19.4 million , $18.4 million and $6.6 million , respectively. The weighted-average per unit or share fair value was $13.77 , $9.60 and $13.36 for grants issued in 2017, 2016 and 2015, respectively. The per unit or share granted in 2017 was estimated on the respective dates of grant using the following assumptions: an expected life of 2.8 years, a dividend rate of 2.05% , a risk-free interest rate of 1.55% and an expected price volatility of 20.0% . The per unit or share granted in 2016 was estimated on the respective dates of grant using the following assumptions: an expected life of 2.8 years, a dividend rate of 2.10% , a risk-free interest rate of 0.84% and an expected price volatility of 24.0% . The per unit or share granted in 2015 was estimated on the respective dates of grant using the following assumptions: an expected life of 3.0 and 2.9 years, a dividend rate of 1.90% , a risk-free interest rate of 0.8% and 1.0% , and an expected price volatility between 24.0% and 29.0% . No other stock options, dividend equivalents, or stock appreciation rights were issued or outstanding in 2017, 2016 and 2015. The following is a summary of restricted stock and LTIP unit activity for the year ended December 31, 2017 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2016 107,793 2,881,629 $ 10.01 Vested (48,900 ) (588,367 ) 11.97 Granted 34,407 1,372,574 13.77 Forfeited or unearned (2,509 ) (77,227 ) 5.36 Unvested balance at December 31, 2017 90,791 3,588,609 $ 11.20 The total fair value of LTIP units and restricted stock that vested during 2017, 2016 and 2015 was $7.6 million , $5.1 million and $3.5 million , respectively. The LTIP unit and restricted stock award agreements will immediately vest when a grantee attains the (i) age of 60 and (ii) the date on which grantee has first completed ten years of continuous service with us or our affiliates. For award agreements that qualify, we recognize noncash compensation expense on the grant date for the time-based awards and ratably over the vesting period for the performance-based awards, and accordingly we recognized $1.0 million , $0.7 million and $0.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Unrecognized compensation expense was $0.8 million at December 31, 2017, which will be recognized over a weighted average period of 2.2 years . For the remainder of the LTIP unit and restricted stock awards, we recognize noncash compensation expense ratably over the vesting period, and accordingly, we recognized $13.1 million , $9.0 million and $5.0 million in noncash compensation expense for the years ended December 31, 2017, 2016 and 2015, respectively. Unrecognized compensation expense was $23.2 million at December 31, 2017, which will be recognized over a weighted average period of 2.3 years . Earnings Per Share Earnings per share for the years ended December 31, 2017 , 2016 and 2015 is computed as follows (amounts in thousands, except per share amounts): For the Year Ended December 31, 2017 2016 2015 Numerator - Basic: Net income $ 118,253 $ 107,250 $ 79,928 Private perpetual preferred unit distributions (936 ) (936 ) (936 ) Net income attributable to non-controlling interests (54,670 ) (54,858 ) (45,262 ) Earnings allocated to unvested shares (36 ) (36 ) (24 ) Net income attributable to common stockholders - basic $ 62,611 $ 51,420 $ 33,706 Numerator - Diluted: Net income $ 118,253 $ 107,250 $ 79,928 Private perpetual preferred unit distributions (936 ) (936 ) (936 ) Earnings allocated to unvested shares (36 ) (36 ) (550 ) Net income attributable to common stockholders - diluted $ 117,281 $ 106,278 $ 78,442 Denominator: Weighted average shares outstanding - basic 158,380 133,881 114,245 Operating partnership units 138,075 142,967 151,669 Effect of dilutive securities: Stock-based compensation plans 775 454 707 Exchangeable senior notes 819 266 — Weighted average shares outstanding - diluted 298,049 277,568 266,621 Earnings per share - basic $ 0.40 $ 0.38 $ 0.30 Earnings per share - diluted $ 0.39 $ 0.38 $ 0.29 There were 834,267 , 800,746 , and zero antidilutive shares for the years ended December 31, 2017, 2016 and 2015, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions QIA Securities Purchase Agreement On August 23, 2016, we entered into a securities purchase agreement (the “Securities Purchase Agreement”) with QIA, pursuant to which QIA purchased from us 29,610,854 shares (the “Shares”) of our Class A common stock, par value $0.01 per share, at a purchase price of $21.00 per share. The Shares represented a 9.9% fully diluted economic interest in us (inclusive of all outstanding common operating partnership units and long term incentive plan units of Empire State Realty OP, L.P., our operating partnership). We received approximately $621.8 million in gross proceeds at the closing for the purchase and sale of the Shares (the “Closing”). Stockholders Agreement In connection with the sale of the Shares to QIA, we and QIA entered into a stockholders agreement, dated as of August 23, 2016 (the “Stockholders Agreement”), which sets forth certain rights and obligations of us and QIA, relating to QIA’s ownership of our Class A common stock, including the following: QIA could not transfer any Shares during the six-month period that followed the Closing, and not transfer more than 50% of the Shares during the period that began six months after the Closing and ended on the one-year anniversary of the Closing. All restrictions on transfer pursuant to the Stockholders Agreement have now lapsed. QIA has agreed to limit its voting power on all matters coming before our stockholders (whether at a meeting or by written consent) to no more than 9.9% of the total number of votes entitled to be cast on such matter. Any shares of Class A common stock held by QIA in excess of such 9.9% threshold will be voted in the same manner and proportion as the votes cast by all other stockholders on such matters. QIA granted our Board of Directors an irrevocable proxy to vote in such manner any shares of Class A common stock it holds in excess of such 9.9% . Further, QIA has agreed to vote all of its shares of Class A common stock up to the 9.9% threshold in favor of the election of each member of any slate of director nominees recommended by our Board of Directors. In connection with any new issuance by us of common equity securities, for so long as QIA maintains at least a 5.0% fully diluted economic interest in us and remains in material compliance with the terms of the Stockholders Agreement, QIA will have the right (but not the obligation) to purchase its pro rata share of such new equity securities in the form of newly issued shares of Class A common stock. These “top up” rights are generally exercisable on a quarterly basis, or sooner if we or the operating partnership issues new equity securities in an issuance in excess of $1.0 million . For an initial period of five years from the date of the Closing, to the extent QIA remains in material compliance with the terms of the Stockholders Agreement, QIA will have the right of first offer to co-invest with us as a joint venture partner in real estate investment opportunities initiated by us where we have elected, at our discretion, to seek a joint venture partner. The right of first offer period will be extended for a 30-month term if at least one joint venture transaction is consummated among us and QIA during the initial five-year term, and will be extended for a further 30-month term if at least one joint venture transaction is consummated during such initial 30-month extension term. Subject to certain minimum thresholds and conditions, we will indemnify QIA for certain applicable U.S. federal and state taxes payable by QIA in connection with dividends paid by us on the Shares (and any “top up” shares) that are attributable to capital gains from the sale or exchange of any U.S. real property interests. Our obligation to indemnify QIA will terminate one year following the date on which the sum of the Shares and any “top up” shares then owned by QIA falls below 10% of our outstanding common shares. Registration Rights Agreement In connection with the sale of the Shares to QIA, we and QIA entered into a registration rights agreement, dated as of August 23, 2016 (the “Registration Rights Agreement”), which required us, among other things, to file with the SEC within 180 days following the Closing, a resale shelf registration statement providing for the resale of the Shares. We filed the resale shelf registration statement with the SEC on February 2, 2017 and renewed it on August 3, 2017. In addition, QIA will be entitled to cause us to include in the registration statement such additional “top up” shares of Class A common stock as QIA may acquire from time to time in the future, up to a 9.9% fully diluted economic interest in us. The registration rights are subject to certain conditions and limitations, including restrictions on sales of shares by the holder in connection with certain public offerings and our right to delay or withdraw a registration statement under certain circumstances. We will generally pay all registration expenses in connection with our obligations under the Registration Rights Agreement. Tax Protection Agreement In 2013, we entered into a tax protection agreement with Anthony E. Malkin and Peter L. Malkin that is intended to protect to a limited extent the Malkin Group and an additional third party investor in Metro Center (who was one of the original landowners and was involved in the development of the property) against certain tax consequences arising from a transaction involving one of four properties, which we refer to in this section as the protected assets. First, this agreement provides that our operating partnership will not sell, exchange, transfer or otherwise dispose of such protected assets, or any interest in a protected asset, until (i) October 7, 2025, with respect to one protected asset, First Stamford Place, and (ii) the later of (x) October 7, 2021 and (y) the death of both Peter L. Malkin and Isabel W. Malkin, who are 84 and 81 years old, respectively, for the three other protected assets, Metro Center, 10 Bank Street and 1542 Third Avenue, unless: (1) Anthony E. Malkin consents to the sale, exchange, transfer or other disposition; or (2) our operating partnership delivers to each protected party thereunder a cash payment intended to approximate the tax liability arising from the recognition of the pre-contribution built-in gain resulting from the sale, exchange, transfer or other disposition of such protected asset (with the pre-contribution “built-in gain” being not more than the taxable gain that would have been recognized by such protected party if the protected asset been sold for fair market value in a taxable transaction at the time of the consolidation) plus an additional amount so that, after the payment of all taxes on amounts received pursuant to the agreement (including any tax liability incurred as a result of receiving such payment), the protected party retains an amount equal to such protected party’s total tax liability incurred as a result of the recognition of the pre-contribution built-in gain pursuant to such sale, exchange, transfer or other disposition; or (3) the disposition does not result in a recognition of any built-in gain by the protected party. Second, with respect to the Malkin Group, including Anthony E. Malkin and Peter L. Malkin, and one additional third party investor in Metro Center (who was one of the original landowners and was involved in the development of the property), to protect against gain recognition resulting from a reduction in such continuing investor’s share of the operating partnership liabilities, the agreement provides that during the period from October 7, 2013 until such continuing investor owns less than the aggregate number of operating partnership units and shares of common stock equal to 50% of the aggregate number of such units and shares such investor received in the formation transactions, which we refer to in this section as the tax protection period, our operating partnership will (i) refrain from prepaying any amounts outstanding under any indebtedness secured by the protected assets and (ii) use its commercially reasonable efforts to refinance such indebtedness at or prior to maturity at its current principal amount, or, if our operating partnership is unable to refinance such indebtedness at its current principal amount, at the highest principal amount possible. The agreement also provides that, during the tax protection period, our operating partnership will make available to such continuing investors the opportunity (i) to enter into a “bottom dollar” guarantee of their allocable share of $160.0 million of aggregate indebtedness of our operating partnership meeting certain requirements or (ii) in the event our operating partnership has recourse debt outstanding and such a continuing investor agrees, in lieu of guaranteeing debt pursuant to clause (i) above, to enter into a deficit restoration obligation, in each case, in a manner intended to provide an allocation of operating partnership liabilities to the continuing investor. In the event that a continuing investor guarantees debt of our operating partnership, such continuing investor will be responsible, under certain circumstances, for the repayment of the guaranteed amount to the lender in the event that the lender would otherwise recognize a loss on the loan, such as, for example, if property securing the loan was foreclosed and the value was not sufficient to repay a certain amount of the debt. A deficit restoration obligation is a continuing investor’s obligation, under certain circumstances, to contribute a designated amount of capital to our operating partnership upon our operating partnership’s liquidation in the event that the assets of our operating partnership are insufficient to repay our operating partnership liabilities. Because we expect that our operating partnership will at all times have sufficient liabilities to allow it to meet its obligations to allocate liabilities to its partners that are protected parties under the tax protection agreement, our operating partnership’s indemnification obligation with respect to “certain tax liabilities” would generally arise only in the event that the operating partnership disposes in a taxable transaction of a protected asset within the period specified above in a taxable transaction. In the event of such a disposition, the amount of our operating partnership’s indemnification obligation would depend on several factors, including the amount of “built-in gain,” if any, recognized and allocated to the indemnified partners with respect to such disposition and the effective tax rate to be applied to such gain at the time of such disposition. The operating partnership agreement requires that allocations with respect to such acquired property be made in a manner consistent with Section 704(c) of the Code. Treasury Regulations issued under Section 704(c) of the Code provide partnerships with a choice of several methods of allocating book-tax differences. Under the tax protection agreement, our operating partnership has agreed to use the “traditional method” for accounting for book-tax differences for the properties acquired by our operating partnership in the consolidation. Under the traditional method, which is the least favorable method from our perspective, the carryover basis of the acquired properties in the hands of our operating partnership (i) may cause us to be allocated lower amounts of depreciation and other deductions for tax purposes than would be allocated to us if all of the acquired properties were to have a tax basis equal to their fair market value at the time of acquisition and (ii) in the event of a sale of such properties, could cause us to be allocated gain in excess of its corresponding economic or book gain (or taxable loss that is less than its economic or book loss), with a corresponding benefit to the partners transferring such properties to our operating partnership for interests in our operating partnership. Registration Rights We entered into a registration rights agreement with certain persons receiving shares of our common stock or operating partnership units in the formation transactions, including certain members of our senior management team and our other continuing investors. In connection therewith, we have filed, and are obligated to maintain the effectiveness of, an automatically effective shelf registration statement, along with a prospectus supplement, with respect to, among other things, shares of our Class A common stock that may be issued upon redemption of operating partnership units or issued upon conversion of shares of Class B common stock to continuing investors in the public existing entities. Pursuant to the registration rights agreement, under certain circumstances, we will also be required to undertake an underwritten offering upon the written request of the Malkin Group, which we refer to as the holder, provided (i) the registrable shares to be registered in such offering will have a market value of at least $150.0 million , (ii) we will not be obligated to effect more than two underwritten offerings during any 12-month period; and (iii) the holder will not have the ability to effect more than four underwritten offerings. In addition, if we file a registration statement with respect to an underwritten offering for our own account or on behalf of the holder, the holder will have the right, subject to certain limitations, to register such number of registrable shares held by him, her or it as each such holder requests. With respect to underwritten offerings on behalf of the holder, we will have the right to register such number of primary shares as we request; provided, however, that if cut backs are required by the managing underwriters of such an offering, our primary shares shall be cutback first (but in no event will our shares be cut back to less than $25.0 million ). We have also agreed to indemnify the persons receiving rights against specified liabilities, including certain potential liabilities arising under the Securities Act, or to contribute to the payments such persons may be required to make in respect thereof. We have agreed to pay all of the expenses relating to the registration and any underwritten offerings of such securities, including, without limitation, all registration, listing, filing and stock exchange or FINRA fees, all fees and expenses of complying with securities or “blue sky” laws, all printing expenses and all fees and disbursements of counsel and independent public accountants retained by us, but excluding underwriting discounts and commissions, any out-of-pocket expenses (except we will pay any holder’s out-of-pocket fees (including disbursements of such holder’s counsel, accountants and other advisors) up to $25,000 in the aggregate for each underwritten offering and each filing of a resale shelf registration statement or demand registration statement), and any transfer taxes. Employment Agreement and Change in Control Severance Agreements We entered into an employment agreement with Anthony E. Malkin, which provides for salary, bonuses and other benefits, including among other things, severance benefits upon a termination of employment under certain circumstances and the issuance of equity awards. In addition, we entered into change in control severance agreements with Thomas P. Durels, David A. Karp, Thomas N. Keltner, Jr. and John B. Kessler. Indemnification of Our Directors and Officers We entered into indemnification agreements with each of our directors, executive officers, chairman emeritus and certain other parties, providing for the indemnification by us for certain liabilities and expenses incurred as a result of actions brought, or threatened to be brought, against (i) our directors, executive officers and chairman emeritus and (ii) our executive officers, chairman emeritus and certain other parties who are former members, managers, securityholders, directors, limited partners, general partners, officers or controlling persons of our predecessor in such capacities. Excluded Properties and Businesses The Malkin Group, including Anthony E. Malkin, our Chairman and Chief Executive Officer, owns non-controlling interests in, and Anthony E. Malkin and Peter L. Malkin control the general partners or managers of, the entities that own interests in seven multi-family properties, five net leased retail properties, (including one single tenant retail property in Greenwich, Connecticut), and a parcel that is being developed for residential use. The Malkin Group also owns non-controlling interests in one Manhattan office property, two Manhattan retail properties and several retail properties outside of Manhattan, none of which were contributed to us in the formation transactions. We refer to the non-controlling interests described above collectively as the excluded properties. In addition, the Malkin Group owns interests in two mezzanine and senior equity funds, an industrial fund, and five residential properties, and which we refer to collectively as the excluded businesses. Other than the Greenwich retail property, we do not believe that the excluded properties or the excluded businesses are consistent with our portfolio geographic or property type composition, management or strategic direction. Pursuant to management and/or service agreements with the owners of interests in those excluded properties and services agreements with the five residential property managers and the managers of certain other excluded businesses which historically were managed by affiliates of our predecessor, we are designated as the asset manager (supervisor) and/or property manager of the excluded properties and will provide services to the owners of certain of the excluded properties and the five residential property managers and provide services and access to office space to the existing managers of the other excluded businesses. As the manager or service provider, we are paid a management or other fee with respect to those excluded properties and excluded businesses where our predecessor had previously received a management fee on the same terms as the fee paid to our predecessor, and reimbursed for our costs in providing the management and other services to those excluded properties and businesses where our predecessor had not previously received a management fee. Our management of the excluded properties and provision of services to the five residential property managers and the existing managers of the other excluded businesses represent a minimal portion of our overall business. There is no established time period in which we will manage such properties or provide services to the owners of certain of the excluded properties and the five residential property managers and provide services and access to office space to the existing managers of the other excluded businesses; and Peter L. Malkin and Anthony E. Malkin expect to sell certain of these properties or unwind certain of these businesses over time. We are not precluded from acquiring all or certain interests in the excluded properties or businesses. If we were to attempt any such acquisition, we anticipate that Anthony E. Malkin, our Chairman and Chief Executive Officer, will not participate in the negotiation process on our behalf with respect to our potential acquisition of any of these excluded properties or businesses, and the approval of a majority of our independent directors will be required to approve any such acquisition. Services are and were provided by us to excluded properties and businesses. These transactions are reflected in our consolidated statements of income as third-party management and other fees. We earned asset management (supervisory) and service fees from excluded properties and businesses of $1.1 million , $1.4 million and $1.8 million during the years ended December 31, 2017 , 2016 and 2015, respectively. We earned property management fees from excluded properties of $0.3 million , $0.4 million and $0.3 million during the years ended December 31, 2017 , 2016 and 2015, respectively. Other We were reimbursed at allocable cost for 647 square feet of shared office space, equipment, and administrative support shared with us in our corporate offices, as was done prior to our formation, and we received rent generally at market rental rate for 3,074 square feet of leased space, from entities affiliated with Anthony E. Malkin at one of our properties. Total revenue aggregated $0.2 million and $0.2 million , for the years ended December 31, 2016 and 2015, respectively. During August 2016, such entities moved from the previously shared office and leased spaces to relocate to a new 5,351 square foot leased space at one of our properties, paying rent generally at a market rental rate. Under such new lease, the tenant has the right to cancel such lease without special payment on 90 days’ notice. We now have a shared use agreement with such tenant, to occupy a portion of the leased premises as the office location for Peter L. Malkin, our chairman emeritus and employee, utilizing approximately 15% of the space, for which we pay an allocable pro rata share of the cost to such tenant. We also have agreements with these entities and excluded properties and businesses to provide them with general computer-related support. Total revenue aggregated $0.4 million and $0.1 million for the years ended December 31, 2017 and 2016, respectively. During 2016 and in connection with our office move, Peter L. Malkin purchased miscellaneous furniture and artwork from us at their appraised value of $23,300 . Remaining office furniture was disposed. One of our directors, James D. Robinson IV, is a general partner in an investment fund, which owns more than a 10% economic and voting interest in one of our tenants, OnDeck Capital, with an annualized rent of $5.8 million and $5.7 million as of December 31, 2017 and 2016, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes TRS Holdings and Observatory TRS are taxable entities and their consolidated provision for income taxes consisted of the following for the years ended December 31, 2017 , 2016 and 2015 (amounts in thousands): For the Year Ended December 31, 2017 2016 2015 Current: Federal $ (3,923 ) $ (3,632 ) $ (2,714 ) State and local (2,304 ) (2,055 ) (1,502 ) Total current (6,227 ) (5,687 ) (4,216 ) Deferred: Federal (446 ) (291 ) 169 State and local — (168 ) 98 Total deferred (446 ) (459 ) 267 Income tax expense $ (6,673 ) $ (6,146 ) $ (3,949 ) In December 2017, the Tax Cuts and Jobs Act (the “TCJA”) was enacted. The TCJA includes a number of changes to existing U.S. tax laws, most notably a reduction of the U.S. corporate income tax rate from 35 percent to 21 percent, effective January 1, 2018. We measure deferred tax assets using enacted tax rates that will apply in the years in which the temporary differences are expected to be recovered or paid. Accordingly, our deferred tax assets were remeasured to reflect the reduction in the U.S. corporate income tax rate, resulting in a $0.4 million increase in income tax expense for the year ended December 31, 2017 and a corresponding decrease of the same amount in our deferred assets as of December 31, 2017. The effective income tax rate is 48.5% , 44.8% and 44.7% for the years ended December 31, 2017 , 2016 and 2015, respectively. The actual tax provision differed from that computed at the federal statutory corporate rate as follows (amounts in thousands): For the Year Ended December 31, 2017 2016 2015 Federal tax expense at 34% statutory rate $ (4,684 ) $ (4,629 ) $ (3,003 ) State income taxes, net of federal benefit (1,543 ) (1,517 ) (946 ) Corporate income tax rate adjustment (446 ) — — Income tax expense $ (6,673 ) $ (6,146 ) $ (3,949 ) The income tax effects of temporary differences that give rise to deferred tax assets are presented below as of December 31, 2017 , 2016 and 2015 (amounts in thousands): 2017 2016 2015 Deferred tax assets: Deferred revenue on unredeemed observatory admission ticket sales $ 1,395 $ 198 $ 267 Deferred tax assets at December 31, 2017, 2016 and 2015, respectively, are attributable to the inclusion of deferred revenue on Observatory admission ticket sales not redeemed at year-end in determining income for tax reporting purposes. No valuation allowance has been recorded against the deferred tax asset because the Company believes that the deferred tax asset will, more likely than not, be realized. This determination is based on the Observatory TRS’s anticipated future taxable income and the reversal of the deferred tax asset. At December 31, 2017 , 2016 and 2015, the TRS entities have no amount of unrecognized tax benefits. For tax years 2017, 2016, 2015 and 2014, the United States federal and state tax returns are open for examination.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting We have identified two reportable segments: (1) Real Estate and (2) Observatory. Our real estate segment includes all activities related to the ownership, management, operation, acquisition, repositioning and disposition of our real estate assets. Our observatory segment operates the 86th and 102nd floor observatories at the Empire State Building. These two lines of businesses are managed separately because each business requires different support infrastructures, provides different services and has dissimilar economic characteristics such as investments needed, stream of revenues and different marketing strategies. We account for intersegment sales and rents as if the sales or rents were to third parties, that is, at current market prices. We include our historical construction operation in "Other," and it includes all activities related to providing construction services to tenants and to other entities within and outside our company. As of March 27, 2015, we no longer solicited new business for our construction management business. We completed all projects that were in progress. The following tables provide components of segment profit for each segment for the years ended December 31, 2017 , 2016 and 2015, as reviewed by management (amounts in thousands): 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 483,944 $ — $ — $ 483,944 Intercompany rental revenue 77,646 — (77,646 ) — Tenant expense reimbursement 73,679 — — 73,679 Observatory revenue — 127,118 — 127,118 Third-party management and other fees 1,400 — — 1,400 Other revenue and fees 26,327 — — 26,327 Total revenues 662,996 127,118 (77,646 ) 712,468 Operating expenses: Property operating expenses 163,531 — — 163,531 Intercompany rent expense — 77,646 (77,646 ) — Ground rent expense 9,326 — — 9,326 General and administrative expenses 50,315 — — 50,315 Observatory expenses — 30,275 — 30,275 Real estate taxes 102,466 — — 102,466 Depreciation and amortization 160,630 80 — 160,710 Total operating expenses 486,268 108,001 (77,646 ) 516,623 Total operating income 176,728 19,117 — 195,845 Interest expense (68,473 ) — — (68,473 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments (289 ) — — (289 ) Income before income taxes 105,809 19,117 — 124,926 Income tax expense (1,306 ) (5,367 ) — (6,673 ) Net income $ 104,503 $ 13,750 $ — $ 118,253 Segment assets $ 3,670,907 $ 260,440 $ — $ 3,931,347 Expenditures for segment assets $ 191,541 $ 36,621 $ — $ 228,162 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 460,653 $ — $ — $ 460,653 Intercompany rental revenue 75,658 — (75,658 ) — Tenant expense reimbursement 73,459 — — 73,459 Observatory revenue — 124,814 — 124,814 Third-party management and other fees 1,766 — — 1,766 Other revenue and fees 17,293 15 — 17,308 Total revenues 628,829 124,829 (75,658 ) 678,000 Operating expenses: Property operating expenses 153,850 — — 153,850 Intercompany rent expense — 75,658 (75,658 ) — Ground rent expense 9,326 — — 9,326 General and administrative expenses 49,078 — — 49,078 Observatory expenses — 29,833 — 29,833 Real estate taxes 96,061 — — 96,061 Acquisition expenses 98 — — 98 Depreciation and amortization 154,817 394 — 155,211 Total operating expenses 463,230 105,885 (75,658 ) 493,457 Total operating income (loss) 165,599 18,944 — 184,543 Interest expense (70,595 ) — — (70,595 ) Loss on early extinguishment of debt (552 ) — — (552 ) Income before income taxes 94,452 18,944 — 113,396 Income tax expense (1,361 ) (4,785 ) — (6,146 ) Net income $ 93,091 $ 14,159 $ — $ 107,250 Segment assets $ 3,641,844 $ 249,109 $ — $ 3,890,953 Expenditures for segment assets $ 197,680 $ — $ — $ 197,680 2015 Real Estate Observatory Other Intersegment Elimination Total Revenues: Rental revenue $ 447,784 $ — $ — $ — $ 447,784 Intercompany rental revenue 68,255 — — (68,255 ) — Tenant expense reimbursement 79,516 — — — 79,516 Observatory revenue — 112,172 — — 112,172 Construction revenue — — 5,696 (3,715 ) 1,981 Third-party management and other fees 2,133 — — — 2,133 Other revenue and fees 14,048 — — — 14,048 Total revenues 611,736 112,172 5,696 (71,970 ) 657,634 Operating expenses: Property operating expenses 158,638 — — — 158,638 Intercompany rent expense — 68,255 — (68,255 ) — Ground rent expense 9,326 — — — 9,326 General and administrative expenses 38,073 — — — 38,073 Observatory expenses — 32,174 — — 32,174 Construction expenses — — 6,539 (3,317 ) 3,222 Real estate taxes 93,165 — — — 93,165 Acquisition expenses 193 — — — 193 Depreciation and amortization 171,035 338 101 — 171,474 Total operating expenses 470,430 100,767 6,640 (71,572 ) 506,265 Total operating income (loss) 141,306 11,405 (944 ) (398 ) 151,369 Interest expense (65,743 ) — — — (65,743 ) Loss on early extinguishment of debt (1,749 ) — — — (1,749 ) Income (loss) before income taxes 73,814 11,405 (944 ) (398 ) 83,877 Income tax (expense) benefit (1,498 ) (2,791 ) 340 — (3,949 ) Net income $ 72,316 $ 8,614 $ (604 ) $ (398 ) $ 79,928 Segment assets $ 3,058,250 $ 241,511 $ 889 $ — $ 3,300,650 Expenditures for segment assets $ 156,543 $ 211 $ — $ — $ 156,754

Summary of Quarterly Financial

Summary of Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information (unaudited)	Summary of Quarterly Financial Information (unaudited) The quarterly results of operations of our company for the years ended December 31, 2017 , 2016 and 2015 are as follows (amounts in thousands): March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Revenues $ 164,954 $ 177,124 $ 187,320 $ 183,070 Operating income $ 36,666 $ 51,434 $ 56,781 $ 50,964 Net income $ 19,145 $ 31,359 $ 35,489 $ 32,260 Net income attributable to common stockholders $ 9,985 $ 16,584 $ 18,806 $ 17,272 Net income per share attributable to common stockholders: Basic and diluted $ 0.06 $ 0.10 $ 0.12 $ 0.11 March 31, 2016 June 30, 2016 September 30, 2016 December 31, 2016 Revenues $ 157,074 $ 165,815 $ 175,848 $ 179,263 Operating income $ 34,114 $ 44,192 $ 53,586 $ 52,651 Net income $ 16,705 $ 24,640 $ 32,897 $ 33,008 Net income attributable to common stockholders $ 7,428 $ 11,089 $ 15,973 $ 16,966 Net income per share attributable to common stockholders: Basic and diluted $ 0.06 $ 0.09 $ 0.12 $ 0.11 March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 Revenues $ 151,882 $ 164,773 $ 175,779 $ 165,200 Operating income $ 23,757 $ 45,039 $ 45,343 $ 37,230 Net income $ 7,888 $ 26,585 $ 26,085 $ 19,370 Net income attributable to common stockholders $ 3,138 $ 11,120 $ 11,220 $ 8,252 Net income per share attributable to common stockholders: Basic and diluted $ 0.03 $ 0.10 $ 0.10 $ 0.07

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II—Valuation and Qualifying Accounts (amounts in thousands) Description Balance At Additions Uncollectible Balance Year ended December 31, 2017 Allowance for doubtful accounts $ 3,723 $ (1,650 ) $ (466 ) $ 1,607 Year ended December 31, 2016 Allowance for doubtful accounts $ 3,037 $ 908 $ (222 ) $ 3,723 Year ended December 31, 2015 Allowance for doubtful accounts $ 1,847 $ 1,298 $ (108 ) $ 3,037

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III - Real Estate and Accumulated Depreciation	Schedule III—Real Estate and Accumulated Depreciation (amounts in thousands) Initial Cost to Cost Capitalized Gross Amount at Development Type Encumbrances Land Building & Improvements Carrying Land Buildings & Total Accumulated Date of Date Life on 111 West 33rd Street, New York, NY office / $ 84,085 $ 13,630 $ 244,461 $ 76,316 n/a $ 13,630 $ 320,777 $ 334,407 $ (31,591 ) 1954 2014 various 1400 Broadway, New York, NY office / 76,085 — 96,338 28,738 — — 125,076 125,076 (27,287 ) 1930 2014 various 1333 Broadway, New York, NY office / 66,590 91,435 120,190 6,143 n/a 91,435 126,333 217,768 (18,481 ) 1915 2013 various 1350 Broadway, New York, NY office / 37,410 — 102,518 21,601 — — 124,119 124,119 (19,330 ) 1929 2013 various 250 West 57th Street, New York, NY office/ — 2,117 5,041 113,414 n/a 2,117 118,455 120,572 (32,729 ) 1921 1953 various 501 Seventh Avenue, New York, NY office/ — 1,100 2,600 92,032 n/a 1,100 94,632 95,732 (39,550 ) 1923 1950 various 1359 Broadway, New York, NY office/ — 1,233 1,809 55,853 n/a 1,233 57,662 58,895 (24,867 ) 1924 1953 various 350 Fifth Avenue (Empire State Building), New York, NY office/ — 21,551 38,934 803,025 n/a 21,551 841,959 863,510 (174,484 ) 1930 2013 various One Grand Central Place, office/ — 7,240 17,490 216,947 n/a 7,222 234,455 241,677 (98,280 ) 1930 1954 various First Stamford Place, Stamford, CT office 178,378 22,952 122,739 53,718 n/a 24,862 174,547 199,409 (76,114 ) 1986 2001 various One Station Place, Stamford, CT (Metro Center) office 93,606 5,313 28,602 13,489 n/a 5,313 42,091 47,404 (29,225 ) 1987 1984 various 383 Main Avenue, Norwalk, CT office 29,572 2,262 12,820 17,534 n/a 2,262 30,354 32,616 (11,933 ) 1985 1994 various 500 Mamaroneck Avenue, Harrison, NY office — 4,571 25,915 22,393 n/a 4,571 48,308 52,879 (21,928 ) 1987 1999 various 10 Bank Street, White Plains, NY office 34,092 5,612 31,803 17,042 n/a 5,612 48,845 54,457 (19,441 ) 1989 1999 various 10 Union Square, New York, NY retail 48,966 5,003 12,866 1,787 n/a 5,003 14,653 19,656 (7,359 ) 1987 1996 various 1542 Third Avenue, New York, NY retail 29,384 2,239 15,266 424 n/a 2,239 15,690 17,929 (7,347 ) 1991 1999 various 1010 Third Avenue, New York, NY and 77 West 55th Street, New York, NY retail 38,996 4,462 15,817 783 n/a 4,462 16,600 21,062 (8,166 ) 1962 1998 various 69-97 Main Street, Westport, CT retail — 2,782 15,766 943 n/a 2,782 16,709 19,491 (6,679 ) 1922 2003 various 103-107 Main Street, Westport, CT retail — 1,243 7,043 182 n/a 1,260 7,208 8,468 (2,109 ) 1900 2006 various Property for development at the Transportation Hub in Stamford CT land — 4,542 — 7,986 — 12,528 — 12,528 — n/a n/a n/a Totals $ 717,164 $ 199,287 $ 918,018 $ 1,550,350 $ — $ 209,182 $ 2,458,473 $ 2,667,655 $ (656,900 ) Empire State Realty Trust, Inc. Notes to Schedule III—Real Estate and Accumulated Depreciation (amounts in thousands) 1 . Reconciliation of Investment Properties The changes in our investment properties for the years ended December 31, 2017, 2016 and 2015 are as follows: 2017 2016 2015 Balance, beginning of year $ 2,458,629 $ 2,276,330 $ 2,139,863 Acquisition of new properties — — — Improvements 228,162 197,680 156,754 Disposals (19,136 ) (15,381 ) (20,287 ) Balance, end of year $ 2,667,655 $ 2,458,629 $ 2,276,330 The unaudited aggregate cost of investment properties for federal income tax purposes as of December 31, 2017 was $2,305,283 . 2 . Reconciliation of Accumulated Depreciation The changes in our accumulated depreciation for the years ended December 31, 2017, 2016 and 2015 are as follows: 2017 2016 2015 Balance, beginning of year $ 556,546 $ 465,584 $ 377,552 Depreciation expense 119,490 106,343 108,319 Disposals (19,136 ) (15,381 ) (20,287 ) Balance, end of year $ 656,900 $ 556,546 $ 465,584 Depreciation of investment properties reflected in the combined statements of income is calculated over the estimated original lives of the assets as follows: Buildings 39 years Building improvements 39 years or useful life Tenant improvements Term of related lease

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and with the rules and regulations of the Securities and Exchange Commission (the "SEC") represent our assets and liabilities and operating results. The consolidated financial statements include our accounts and our wholly owned subsidiaries as well as our operating partnership and its subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Consolidation, Variable Interest Entity	We consolidate entities in which we have a controlling financial interest. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, authority to make decisions, and contractual and substantive participating rights of the partners/members as well as whether the entity is a variable interest entity (“VIE”) and we are the primary beneficiary. The primary beneficiary of a VIE is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. The primary beneficiary is required to consolidate the VIE. Our operating partnership, Empire State Realty OP, L.P., is a variable interest entity of our company, Empire State Realty Trust, Inc. As the operating partnership is already consolidated in the financial statements of Empire State Realty Trust, Inc., the identification of this entity as a variable interest entity had no impact on our consolidated financial statements. We will assess the accounting treatment for each investment we may have in the future. This assessment will include a review of each entity’s organizational agreement to determine which party has what rights and whether those rights are protective or participating. For all VIEs, we will review such agreements in order to determine which party has the power to direct the activities that most significantly impact the entity’s economic performance and benefit. In situations where we or our partner could approve, among other things, the annual budget, or leases that cover more than a nominal amount of space relative to the total rentable space at each property, we would not consolidate the investment as we consider these to be substantive participation rights that result in shared power of the activities that would most significantly impact the performance and benefit of such joint venture investment. A non-controlling interest in a consolidated subsidiary is defined as the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to a parent. Non-controlling interests are required to be presented as a separate component of equity in the consolidated balance sheets and in the consolidated statements of income by requiring earnings and other comprehensive income to be attributed to controlling and non-controlling interests.
Accounting Estimates	Accounting Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to use estimates and assumptions that in certain circumstances affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Significant items subject to such estimates and assumptions include allocation of the purchase price of acquired real estate properties among tangible and intangible assets, determination of the useful life of real estate properties and other long-lived assets, valuation and impairment analysis of commercial real estate properties and other long-lived assets, estimate of tenant expense reimbursements, estimate of percentage of completion on construction contracts, valuation of the allowance for doubtful accounts, and valuation of derivative instruments, senior unsecured notes, mortgage notes payable, unsecured notes, unsecured revolving credit and term loan facilities, and equity based compensation. These estimates are prepared using management’s best judgment, after considering past, current, and expected events and economic conditions. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition Rental Revenue Rental revenue includes base rents that each tenant pays in accordance with the terms of its respective lease and is reported on a straight-line basis over the non-cancellable term of the lease which includes the effects of rent steps and rent abatements under the leases. In general, we commence rental revenue recognition when the tenant takes possession of the leased space or controls the physical use of the leased space and the leased space is substantially ready for its intended use. We account for all of our leases as operating leases. Deferred rent receivables, including free rental periods and leasing arrangements allowing for increased base rent payments, are accounted for in a manner that provides an even amount of fixed lease revenues over the respective non-cancellable lease terms. Differences between rental income recognized and amounts due under the respective lease agreements are recognized as an increase or decrease to deferred rent receivables. In addition to base rent, our tenants also generally will pay their pro rata share of increases in real estate taxes and operating expenses for the building over a base year. In some leases, in lieu of paying additional rent based upon increases in building operating expenses, the tenant will pay additional rent based upon increases in an index such as the Consumer Price Index over the index value in effect during a base year, or contain fixed percentage increases over the base rent to cover escalations. We will recognize rental revenue of acquired in-place above- and below-market leases at their fair values over the terms of the respective leases, including, for below-market leases, fixed option renewal periods, if any. Lease cancellation fees are recognized when the fees are determinable, tenant vacancy has occurred, collectability is reasonably assured, we have no continuing obligation to provide services to such former tenants and the payment is not subject to any conditions that must be met or waived. Total lease cancellation fees for the years ended December 31, 2017 , 2016, and 2015 were $13.6 million , $7.7 million , and $2.0 million , respectively. Such fees are included in other revenues and fees in our consolidated statements of income. Observatory Revenue Revenues from the sale of Observatory tickets are recognized upon admission or ticket expirations. Deferred revenue related to unused and unexpired tickets as of December 31, 2017 and 2016 was $4.1 million and $4.1 million , respectively. Gains on Sale of Real Estate We record a gain on sale of real estate when title is conveyed to the buyer and we have no substantial economic involvement with the property. If the sales criteria for the full accrual method are not met, we defer some or all of the gain recognition and account for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery methods, as appropriate, until the sales criteria are met. Third-Party Management and Other Fees We earn revenue arising from contractual agreements with related party entities for asset and property management services. This revenue is recognized as the related services are performed under the respective agreements in place.
Advertising and Marketing Costs	Advertising and Marketing Costs Advertising and marketing costs are expensed as incurred.
Real Estate Properties and Related Intangible Assets	Real Estate Properties and Related Intangible Assets Land and buildings and improvements are recorded at cost less accumulated depreciation and amortization. The recorded cost includes cost of acquisitions, development and construction and tenant allowances and improvements. Expenditures for ordinary repairs and maintenance are charged to property operating expense as incurred. Significant replacements and betterments which improve or extend the life of the asset are capitalized. Tenant improvements which improve or extend the life of the asset are capitalized. If a tenant vacates its space prior to the contractual termination of its lease, the unamortized balance of any tenant improvements are written off if they are replaced or have no future value. For developed properties, direct and indirect costs that clearly relate to projects under development are capitalized. Costs include construction costs, professional services such as architectural and legal costs, capitalized interest and direct payroll costs. We begin capitalization when the project is probable. The assets relating to the project are stated at cost and are not depreciated. Once construction is completed and the assets are placed in service, the assets are reclassified to the appropriate asset class and depreciated in accordance with the useful lives as indicated below. Capitalization of interest ceases when the asset is ready for its intended use, which is generally near the date that a certificate of occupancy is obtained. Total capitalized interest for the year ended December 31, 2017 was $0.5 million . There was no capitalized interest for the years ended December 31, 2016 and 2015. Depreciation and amortization are computed using the straight-line method for financial reporting purposes. Buildings and improvements are depreciated over the shorter of 39 years, the useful life, or the remaining term of any leasehold interest. Tenant improvement costs, which are included in building and improvements in the consolidated balance sheets, are depreciated over the shorter of (i) the related remaining lease term or (ii) the life of the improvement. Corporate equipment, which is included in “Other assets,” is depreciated over three to seven years. Acquisitions of properties are accounted for utilizing the acquisition method and accordingly the purchase cost is allocated to tangible and intangible assets and liabilities based on their fair values. The fair value of tangible assets acquired is determined by valuing the property as if it were vacant, applying methods similar to those used by independent appraisers of income-producing property. The resulting value is then allocated to land, buildings and improvements, and tenant improvements based on our determination of the fair value of these assets. The assumptions used in the allocation of fair values to assets acquired are based on our best estimates at the time of evaluation. Fair value is assigned to above-market and below-market leases based on the difference between (a) the contractual amounts to be paid by the tenant based on the existing lease and (b) our estimate of current market lease rates for the corresponding in-place leases, over the remaining terms of the in-place leases. Capitalized above-market lease amounts are amortized as a decrease to rental revenue over the remaining terms of the respective leases. Capitalized below-market lease amounts are amortized as an increase to rental revenue over the remaining terms of the respective leases. If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The aggregate value of other acquired intangible assets consists of acquired ground leases and acquired in-place leases and tenant relationships. The fair value allocated to acquired in-place leases consists of a variety of components including, but not necessarily limited to: (a) the value associated with avoiding the cost of originating the acquired in-place leases (i.e. the market cost to execute a lease, including leasing commissions and legal fees, if any); (b) the value associated with lost revenue related to tenant reimbursable operating costs estimated to be incurred during the assumed lease-up period (i.e. real estate taxes, insurance and other operating expenses); (c) the value associated with lost rental revenue from existing leases during the assumed lease-up period; and (d) the value associated with any other inducements to secure a tenant lease. We assess the potential for impairment of our long-lived assets, including real estate properties, annually or whenever events occur or a change in circumstances indicate that the recorded value might not be fully recoverable. We determine whether impairment in value has occurred by comparing the estimated future undiscounted cash flows expected from the use and eventual disposition of the asset to its carrying value. If the undiscounted cash flows do not exceed the carrying value, the real estate is adjusted to fair value and an impairment loss is recognized. Assets held for sale are recorded at the lower of cost or fair value less costs to sell. We do not believe that the value of any of our properties and intangible assets were impaired during the years ended December 31, 2017, 2016 and 2015.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, government money markets, demand deposits with financial institutions and short-term liquid investments with original maturities of three months or less when purchased. Cash and cash equivalents held at major commercial banks may at times exceed the Federal Deposit Insurance Corporation limit. To date, we have not experienced any losses on our invested cash. Restricted Cash Restricted cash consists of amounts held for tenants in accordance with lease agreements such as security deposits and amounts held by lenders and/or escrow agents to provide for future real estate tax expenditures and insurance expenditures, tenant vacancy related costs and debt service obligations.
Tenant and Other Receivables	Tenant and Other Receivables Tenant and other receivables, other than deferred rent receivable, are generally expected to be collected within one year.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts We maintain an allowance against tenant and other receivables and deferred rents receivables for future potential tenant credit losses. The credit assessment is based on the estimated accrued rental revenue that is recoverable over the term of the respective lease. The computation of this allowance is based on the tenants’ payment history and current credit status. If our estimate of collectability differs from the cash received, then the timing and amount of our reported revenue could be impacted. Bad debt expense is included in operating expenses on our consolidated statements of income and includes the impact of changes in the allowance for doubtful accounts on our consolidated balance sheets.
Deferred Leasing Costs and Deferred Financing Costs	Deferred Leasing Costs Deferred leasing costs consist of fees and direct costs incurred to initiate and renew leases, are amortized on a straight-line basis over the related lease term and the expense is included in depreciation and amortization in our consolidated statements of income. Upon the early termination of a lease, unamortized deferred leasing costs are charged to expense. Deferred Financing Costs Fees and costs incurred to obtain long-term financing have been deferred and are amortized as a component of interest expense in our consolidated statements of income over the life of the respective long-term financing on the straight-line method which approximates the effective interest method. Unamortized deferred financing costs are expensed when the associated debt is refinanced or repaid before maturity. Costs incurred in seeking debt, which do not close, are expensed in the period in which it is determined that the financing will not close.
Equity Method Investments	Equity Method Investments We account for investments under the equity method of accounting where we do not have control but have the ability to exercise significant influence. Under this method, investments are recorded at cost, and the investment accounts are adjusted for our share of the entities’ income or loss and for distributions and contributions. Equity income (loss) is allocated based on the portion of the ownership interest that is controlled by us. The agreements may designate different percentage allocations among investors for profits and losses; however, our recognition of the entity’s income or loss generally follows the entity’s distribution priorities, which may change upon the achievement of certain investment return thresholds. To the extent that we contributed assets to an entity, our investment in the entity is recorded at cost basis in the assets that were contributed to the entity. Upon contributing assets to an entity, we make a judgment as to whether the economic substance of the transaction is a sale. If so, gain or loss is recognized on the portion of the asset to which the other partners in the entity obtain an interest. To the extent that the carrying amount of these investments on our combined balance sheets is different than the basis reflected at the entity level, the basis difference would be amortized over the life of the related asset and included in our share of equity in net income of the entity. On a periodic basis, we assess whether there are any indicators that the carrying value of our investments in entities may be impaired on an other than temporary basis. An investment is impaired only if management’s estimate of the fair value of the investment is less than the carrying value of the investment on an other than temporary basis. To the extent impairment has occurred, the loss shall be measured as the excess of the carrying value of the investment over the fair value of the investment. As of December 31, 2017 and 2016, we had no equity method investments.
Goodwill	Goodwill Goodwill is tested annually for impairment and is tested for impairment more frequently if events and circumstances indicate that the asset might be impaired. An impairment loss is recognized to the extent that the carrying amount, including goodwill, exceeds the reporting unit’s fair value and the implied fair value of goodwill is less than the carrying amount of that goodwill. Non-amortizing intangible assets, such as trade names and trademarks, are subject to an annual impairment test based on fair value and amortizing intangible assets are tested whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.
Fair Value	Fair Value Fair value is a market-based measurement, not an entity-specific measurement, and should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, the Financial Accounting Standards Board ("FASB") guidance establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within levels one and two of the hierarchy) and the reporting entity's own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the hierarchy). The methodologies used for valuing financial instruments have been categorized into three broad levels as follows: Level 1 - Quoted prices in active markets for identical instruments. Level 2 - Valuations based principally on other observable market parameters, including: • Quoted prices in active markets for similar instruments; • Quoted prices in less active or inactive markets for identical or similar instruments; • Other observable inputs (such as risk free interest rates, yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates); and • Market corroborated inputs (derived principally from or corroborated by observable market data). Level 3 - Valuations based significantly on unobservable inputs, including: • Valuations based on third-party indications (broker quotes or counterparty quotes) which were, in turn, based significantly on unobservable inputs or were otherwise not supportable; and • Valuations based on internal models with significant unobservable inputs. These levels form a hierarchy. We follow this hierarchy for our financial instruments measured or disclosed at fair value on a recurring and nonrecurring basis and other required fair value disclosures. The classifications are based on the lowest level of input that is significant to the fair value measurement. We use the following methods and assumptions in estimating fair value disclosures for financial instruments. Cash and cash equivalents, restricted cash, tenant and other receivables, prepaid expenses and other assets, deferred revenue, tenant security deposits, accounts payable and accrued expenses carrying values approximate their fair values due to the short term maturity of these instruments. The fair value of our senior unsecured notes - exchangeable was derived from quoted prices in active markets and is classified as Level 2 since trading volumes are low. The fair value of derivative instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Although the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by ourselves and our counterparties. The impact of such credit valuation adjustments, determined based on the fair value of each individual contract, was not significant to the overall valuation. As a result, all of our derivatives were classified as Level 2 of the fair value hierarchy. The fair value of our mortgage notes payable, unsecured revolving credit and term loan facility, and senior unsecured notes - Series A, B, C and D which are determined using Level 3 inputs, are estimated by discounting the future cash flows using current interest rates at which similar borrowings could be made to us.
Derivative Instruments	Derivative Instruments We are exposed to the effect of interest rate changes and manage these risks by following policies and procedures including the use of derivatives. To manage exposure to interest rates, derivatives are used primarily to fix the rate on debt based on floating-rate indices. We also hedge exposure to the variability in future cash flows for forecast transactions over a maximum period of 11 months (excluding forecast transactions related to the payment of variable interest on existing financial instruments). We record all derivatives on the balance sheet at fair value. We incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. We measure the credit risk of our derivative instruments that are subject to master netting agreements on a net basis by counterparty portfolio. For derivatives that qualify as cash flow hedges, we report the gain or loss on the derivative designated as a hedge as part of other comprehensive income (loss) and subsequently reclassify the gain or loss into income in the period that the hedged transaction affects income.
Income Taxes	Income Taxes We elected to be taxed as a REIT under sections 856 through 860 of the Internal Revenue Code of 1986, as amended, (the "Code"), commencing with the taxable year ended December 31, 2013 and believe we qualify as a REIT at December 31, 2017. REITs are subject to a number of organizational and operational requirements, including a requirement that 90% of ordinary “REIT taxable income” (as determined without regard to the dividends paid deduction or net capital gains) be distributed. As a REIT, we will generally not be subject to U.S. federal income tax to the extent that we meet the organizational and operational requirements and our distributions equal or exceed REIT taxable income. For all periods subsequent to the effective date of our REIT election, we have met the organizational and operational requirements and distributions have exceeded net taxable income. Accordingly, no provision has been made for federal and state income taxes. We have elected to treat ESRT Observatory TRS, L.L.C., our subsidiary which holds our observatory operations, and ESRT Holdings TRS, L.L.C., our subsidiary that holds our third party management, construction (through cessation of our construction business in the first quarter of 2015), restaurant, cafeteria, health clubs and certain cleaning operations, as taxable REIT subsidiaries. Taxable REIT subsidiaries may participate in non-real estate activities and/or perform non-customary services for tenants and their operations are generally subject to regular corporate income taxes. Our taxable REIT subsidiaries accounts for its income taxes in accordance with GAAP, which includes an estimate of the amount of taxes payable or refundable for the current year and deferred tax liabilities and assets for the future tax consequences of events that have been recognized in our financial statements or tax returns. The calculation of the taxable REIT subsidiaries' tax provisions may require interpreting tax laws and regulations and could result in the use of judgments or estimates which could cause its recorded tax liability to differ from the actual amount due. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The taxable REIT subsidiaries periodically assess the realizability of deferred tax assets and the adequacy of deferred tax liabilities, including the results of local, state, or federal statutory tax audits or estimates and judgments used. We apply provisions for measuring and recognizing tax benefits associated with uncertain income tax positions. Penalties and interest, if incurred, would be recorded as a component of income tax expense. As of December 31, 2017 and 2016, we do not have a liability for uncertain tax positions. As of December 31, 2017 , the tax years ended December 31, 2014 through December 31, 2017 remain open for an audit by the Internal Revenue Service, state or local authorities.
Share-Based Compensation	Share-Based Compensation Share-based compensation is measured at the fair value of the award on the date of grant and recognized as an expense on a straight-line basis over the vesting period. The determination of fair value of these awards is subjective and involves significant estimates and assumptions including expected volatility of our stock, expected dividend yield, expected term, and assumptions of whether these awards will achieve parity with other operating partnership units or achieve performance thresholds. We believe that the assumptions and estimates utilized are appropriate based on the information available to management at the time of grant.
Per Share Data	Per Share Data Basic and diluted earnings per share are computed based upon the weighted average number of shares outstanding during the respective period.
Segment Reporting	Segment Reporting We have identified two reportable segments: (1) Real Estate and (2) Observatory. Our real estate segment includes all activities related to the ownership, management, operation, acquisition, repositioning and disposition of our real estate assets. Our observatory segment operates the 86th and 102nd floor observatories at the Empire State Building. These two lines of businesses are managed separately because each business requires different support infrastructures, provides different services and has dissimilar economic characteristics such as investments needed, stream of revenues and different marketing strategies. We account for intersegment sales and rent as if the sales or rent were to third parties, that is, at current market prices. We include our construction operation in "Other" and it includes all activities related to providing construction services to tenants and to other entities within and outside our company. As of March 27, 2015, we no longer solicited new business for our construction management business. We completed all projects that were in progress.
Reclassification	Reclassification Certain prior year balances have been reclassified to conform to our current year presentation. The 2016 and 2015 balance of interest expense relating to loss on early extinguishment of debt has been reclassified and presented separately on the consolidated statements of income.
Recently Issued or Adopted Accounting Standards	Recently Issued or Adopted Accounting Standards During August 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which amends its hedge accounting model to enable entities to better portray their risk management activities in the financial statements. The amendments expand an entity’s ability to hedge nonfinancial and financial risk components and reduce complexity in fair value hedges of interest rate risk. ASU No. 2017-12 eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. It also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU No. 2017-12 will be effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period. All transition requirements and elections should be applied to hedging relationships existing on the date of adoption. The effect of adoption should be reflected as of the beginning of the fiscal year of adoption (that is, the initial application date). During 2017, we early adopted ASU No. 2017-02 using a modified retrospective approach for existing and active hedging relationships as of adoption date. The adoption of ASU No. 2017-02 did not have a material impact on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which contain amendments that modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Because these amendments eliminate Step 2 from the goodwill impairment test, they should reduce the cost and complexity of evaluating goodwill for impairment. ASU No. 2017-04 should be applied on a prospective basis and the amendments adopted for the annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which contain amendments to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in ASU No. 2017-01 provide a screen to determine when an integrated set of assets and activities (collectively referred to as a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This screen reduces the number of transactions that need to be further evaluated. If the screen is not met, the amendments (1) require that to be considered a business, a set must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output and (2) remove the evaluation of whether a market participant could replace missing elements. The amendments provide a framework to assist entities in evaluating whether both an input and a substantive process are present. Additionally, these amendments narrow the definition of the term output so that the term is consistent with how outputs are described in Topic 606, Revenue from Contracts with Customers. ASU No. 2017-01 will be effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments should be applied prospectively on or after the effective date. No disclosures are required at transition. We believe that future acquisitions of real estate properties will be considered asset acquisitions. During November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which contain amendments that require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU No. 2016-18 will be effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The amendments should be applied using a retrospective transition method to each period presented. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact on our consolidated financial statements. During August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU No. 2016-15 will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Earlier adoption is permitted including adoption in an interim period. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact on our consolidated financial statements. During June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which contains amendments that replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Earlier adoption as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, is permitted. The amendments must be adopted through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified retrospective approach). We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires that a lessee recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. ASU No. 2016-02 leaves the accounting for leases by lessors largely unchanged from previous GAAP. ASU No. 2016-02 will be effective for fiscal years beginning after December 15, 2018 and subsequent interim periods. The new standard must be adopted using a modified retrospective transition, and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. This ASU is expected to result in the recognition of a right-to-use asset and related liability to account for our future obligations under our ground lease agreements for which we are the lessee. As of December 31, 2017, the remaining contractual payments under our ground lease agreements aggregated $61.3 million . In addition, under ASU 2016-02, lessors may only capitalize incremental direct leasing costs. As a result, we expect that we will no longer capitalize our internal leasing costs and instead will expense these costs as incurred. These costs totaled $2.6 million for the year ended December 31, 2017. We continue to evaluate the impact of adopting this new accounting standard on our consolidated financial statements. During May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). This new standard will replace all current U.S. GAAP guidance related to revenue recognition and eliminate all industry-specific guidance. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance was to be effective beginning in 2017 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. ASU No. 2014-09 was amended in August 2015 by ASU No. 2015-14 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which defers the effective date of ASU No. 2014-09 for all entities by one year. Public business entities, certain not-for-profit entities, and certain employee benefit plans should apply the guidance in ASU No. 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. ASU No. 2014-09 was further amended in December 2016 by ASU No. 2016-20 Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers which contain amendments that are intended to clarify or correct unintended application of the guidance. Those items generally are not expected to have a significant effect on current accounting practice or create a significant administrative cost for most entities. The effective date and transition requirements for the amendments are the same as the effective date and transition requirements for Topic 606. We adopted this standard on January 1, 2018 and it did not have a material impact on our consolidated financial statements.

Deferred Costs, Acquired Leas24

Deferred Costs, Acquired Lease Intangibles and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Deferred Costs, Net	Deferred costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Leasing costs $ 164,751 $ 140,325 Acquired in-place lease value and deferred leasing costs 237,364 253,113 Acquired above-market leases 67,415 74,770 469,530 468,208 Less: accumulated amortization (215,102 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 254,428 $ 272,591 Deferred financing costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Financing costs $ 24,446 $ 23,145 Less: accumulated amortization (7,039 ) (12,241 ) Total deferred financing costs, net $ 17,407 $ 10,904
Schedule of Amortizing Acquired Intangible Assets and Liabilities	Amortizing acquired intangible assets and liabilities consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (28,687 ) (20,856 ) Acquired below-market ground leases, net $ 368,229 $ 376,060 2017 2016 Acquired below-market leases $ (132,026 ) $ (135,026 ) Less: accumulated amortization 65,979 52,726 Acquired below-market leases, net $ (66,047 ) $ (82,300 )
Schedule of Future Amortization Expense and Rental Revenue from Acquired Intangible Assets	We expect to recognize amortization expense and rental revenue from the acquired intangible assets and liabilities as follows (amounts in thousands): For the year ending: Future Ground Rent Amortization Future Amortization Expense Future Rental Revenue 2018 $ 7,831 $ 18,650 $ 6,442 2019 7,831 15,996 6,689 2020 7,831 13,046 3,559 2021 7,831 11,302 2,857 2022 7,831 10,485 3,175 Thereafter 329,074 41,549 12,690 $ 368,229 $ 111,028 $ 35,412

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	Debt consisted of the following as of December 31, 2017 and 2016 (amounts in thousands): As of December 31, 2017 Principal Balance as Principal Balance as Stated Effective (1) Maturity (2) Fixed rate mortgage debt 1333 Broadway $ 66,602 $ 67,656 6.32 % 3.73 % 1/5/2018 1400 Broadway (first lien mortgage loan) 66,632 67,714 6.12 % 3.37 % 2/5/2018 (second lien mortgage loan) 9,172 9,389 3.35 % 3.36 % 2/5/2018 111 West 33rd Street (first lien mortgage loan) 74,045 75,261 6.01 % 3.34 % 4/5/2018 (second lien mortgage loan) 9,369 9,509 6.56 % 3.64 % 4/5/2018 1350 Broadway 37,144 37,764 5.87 % 3.71 % 4/5/2018 Metro Center 93,948 95,985 3.59 % 3.67 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 10 Bank Street 34,602 31,544 4.23 % 4.49 % 6/1/2032 1542 Third Avenue 30,000 17,795 4.29 % 4.64 % 5/1/2027 First Stamford Place (3) 180,000 235,067 4.28 % 4.60 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,710 26,502 4.01 % 4.39 % 1/5/2028 383 Main Avenue 30,000 28,654 4.44 % 4.72 % 6/30/2032 Total mortgage debt 721,224 752,840 Senior unsecured notes - exchangeable 250,000 250,000 2.63 % 3.93 % 8/15/2019 Senior unsecured notes: Series A 100,000 100,000 3.93 % 3.98 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.14 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.23 % 3/27/2030 Series D 115,000 — 4.08 % 4.08 % 1/22/2028 Series E (4) — — 4.26 % — % 3/22/2030 Series F (4) — — 4.44 % — % 3/22/2033 Unsecured revolving credit facility — — (5) (5) 8/29/2021 Unsecured term loan facility 265,000 265,000 (6) (6) 8/29/2022 Total principal 1,701,224 1,617,840 Unamortized (discount) premiums, net of unamortized premiums (discount) (3,370 ) 905 Deferred financing costs, net (9,133 ) (6,414 ) Total $ 1,688,721 $ 1,612,331 ______________ (1) The effective rate is the yield as of December 31, 2017, including the effects of debt issuance costs and the amortization of the fair value of debt adjustment. (2) Pre-payment is generally allowed for each loan upon payment of a customary pre-payment penalty. (3) Represents a $164 million mortgage loan bearing interest of 4.09% and a $16 million loan bearing interest at 6.25% . (4) Senior unsecured notes Series E, totaling $160 million , and Series F, totaling $175 million , will be issued during March 2018. (5) At December 31, 2017, the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at December 31, 2017 was 2.66% . (6) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to a forward interest rate swap agreement, the LIBOR rate is fixed at 2.1485% for the period beginning on August 31, 2017 through maturity. The rate at December 31, 2017 was 3.35%
Schedule of Maturities of Long-term Debt	Aggregate required principal payments at December 31, 2017 are as follows (amounts in thousands): Year Amortization Maturities Total 2018 $ 4,417 $ 262,195 $ 266,612 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 2022 5,455 265,000 270,455 Thereafter 37,890 864,449 902,339 Total principal maturities $ 59,580 $ 1,641,644 $ 1,701,224
Schedule of Deferred Costs, Net	Deferred costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Leasing costs $ 164,751 $ 140,325 Acquired in-place lease value and deferred leasing costs 237,364 253,113 Acquired above-market leases 67,415 74,770 469,530 468,208 Less: accumulated amortization (215,102 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 254,428 $ 272,591 Deferred financing costs, net, consisted of the following at December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Financing costs $ 24,446 $ 23,145 Less: accumulated amortization (7,039 ) (12,241 ) Total deferred financing costs, net $ 17,407 $ 10,904

Accounts Payable and Accrued 26

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following as of December 31, 2017 and 2016 (amounts in thousands): 2017 2016 Accrued capital expenditures $ 71,769 $ 66,620 Accounts payable and accrued expenses 32,509 36,246 Payable to the estate of Leona M. Helmsley (1) — 18,367 Interest rate swap agreements liability 436 5,591 Accrued interest payable 5,687 6,230 Due to affiliated companies 448 1,010 Total accounts payable and accrued expenses $ 110,849 $ 134,064 ___________ (1) Reflects a payable to the estate of Leona M. Helmsley, as required under our formation agreements, for New York City transfer taxes which would have been payable in absence of the estate's exemption from such tax. The taxing authority's final approval of such exemption was issued during the three months ended September 30, 2017, and upon receipt of the confirming documents we made this payment to the estate of Leona M. Helmsley on October 2, 2017.

Financial Instruments and Fai27

Financial Instruments and Fair Values (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Summary of the Terms of Agreements and Fair Values of Derivative Financial Instruments	The table below summarizes the terms of agreements and the fair values of our derivative financial instruments as of December 31, 2017 and 2016 (dollar amounts in thousands): December 31, 2017 December 31, 2016 Derivative Notional Amount Receive Rate Pay Rate Effective Date Expiration Date Asset Liability Asset Liability Interest rate swap $ 265,000 1 Month LIBOR 2.1485 % August 31, 2017 August 24, 2022 $ — $ (436 ) $ — $ (1,634 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.5050 % July 5, 2017 July 5, 2027 — — — (684 ) Interest rate swap (1) (2) 80,000 3 Month LIBOR 2.5050 % July 5, 2017 July 5, 2027 — — — (685 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 224 — Interest rate swap (1) 100,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 223 — Interest rate swap (1) 75,000 3 Month LIBOR 2.4860 % January 5, 2018 January 5, 2028 — — 167 — Interest rate swap (1) 75,000 3 Month LIBOR 2.7620 % June 1, 2018 June 1, 2028 — — — (1,295 ) Interest rate swap (1) 75,000 3 Month LIBOR 2.7620 % June 1, 2018 June 1, 2028 — — — (1,293 ) $ — $ (436 ) $ 614 $ (5,591 ) (1) During 2017, these swaps were terminated in connection with the refinancing of several of our mortgage debt (see Note 4 Debt). As of December 31, 2017, the deferred net losses from these terminated hedges amounted to $15.1 million which is included in accumulated other comprehensive loss relating to net unrealized loss from derivative financial instruments. We will reclassify into earnings, as an increase to interest expense, approximately $1.5 million per year over the 10 -year terms of the related debt due 2027, from the balance that is included in accumulated other comprehensive income on the consolidated balance sheets. (2) During March 2017, $20.0 million of an original notional amount of $100.0 million was terminated. In connection with the partial termination and re-designation of the related cash flow hedges, $0.3 million is recognized as a loss from derivative financial instruments and included in Other Expenses on the consolidated statement of income for the year ended December 31, 2017. There were no losses from derivative financial instruments for the years ended December 31, 2016 and 2015.
Summary of Effect of Derivative Financial Instruments Designated as Cash Flow Hedges	The table below shows the effect of our derivative financial instruments designated as cash flow hedges on accumulated other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015 (amounts in thousands): Effects of Cash Flow Hedges December 31, 2017 December 31, 2016 December 31, 2015 Amount of gain (loss) recognized in other comprehensive income (loss) $ (11,658 ) $ (3,054 ) $ (1,922 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (1,142 ) — — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the consolidated statements of income for the years ended December 31, 2017, 2016 and 2015 (amounts in thousands): Effects of Cash Flow Hedges December 31, 2017 December 31, 2016 December 31, 2015 Total interest (expense) presented on the consolidated statements of income in which the effects of cash flow hedges are recorded $ (68,473 ) $ (70,595 ) $ (65,743 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (1,142 ) — —
Schedule of the Aggregate Carrying Value of Debt and Estimates of Fair Value	The following tables summarize the carrying and estimated fair values of our financial instruments as of December 31, 2017 and 2016 (amounts in thousands): December 31, 2017 Carrying Value Estimated Fair Value Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ — $ — $ — $ — $ — Interest rate swaps included in accounts payable and accrued expenses 436 436 — 436 — Mortgage notes payable 717,164 707,300 — — 707,300 Senior unsecured notes - Exchangeable 244,739 275,723 — 275,723 — Senior unsecured notes - Series A, B, C, D, E and F 463,156 460,352 — — 460,352 Unsecured term loan facility 263,662 265,000 — — 265,000 December 31, 2016 Carrying Value Estimated Fair Value Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 614 $ 614 $ — $ 614 $ — Interest rate swaps included in accounts payable and accrued expenses 5,591 5,591 — 5,591 — Mortgage notes payable 759,016 755,640 — — 755,640 Senior unsecured notes - Exchangeable 241,474 282,435 — 282,435 — Senior unsecured notes - Series A, B, and C 348,914 339,274 — — 339,274 Unsecured term loan facility 262,927 265,000 — — 265,000

Rental Income (Tables)

Rental Income (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule of Future Minimum Payments Receivable for Operating Leases	As of December 31, 2017 , we were entitled to the following future contractual minimum lease payments on non-cancellable operating leases to be received which expire on various dates through 2038 (amounts in thousands): 2018 $ 463,110 2019 451,161 2020 413,745 2021 381,394 2022 351,431 Thereafter 1,649,567 $ 3,710,408

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments	Future minimum lease payments to be paid over the terms of the leases are as follows (amounts in thousands): 2018 $ 1,518 2019 1,518 2020 1,518 2021 1,518 2022 1,518 Thereafter 53,694 Total $ 61,284
Summary of Percent of Total Rental Revenue	For the years ended December 31, 2017 , 2016 and 2015, the six properties listed below accounted for the indicated percentage of total rental revenues. No other property accounted for more than 5.0% of total rental revenues. Year Ended December 31, 2017 2016 2015 Empire State Building 32.0 % 32.6 % 31.4 % One Grand Central Place 13.1 % 12.5 % 12.2 % 111 West 33rd Street 8.6 % 6.8 % 8.3 % 1400 Broadway 7.4 % 7.8 % 7.7 % First Stamford Place 5.4 % 6.4 % 6.5 % 250 West 57th Street 5.2 % 5.3 % 4.8 %
Schedule of Contributions to Multiemployer Plans	Contributions we made to the multi-employer plans for the years ended December 31, 2017, 2016 and 2015 are included in the table below (amounts in thousands): For the Year Ended December 31, Benefit Plan 2017 2016 2015 Pension Plans (pension and annuity)* $ 3,035 $ 3,155 $ 3,077 Health Plans** 8,551 8,280 8,296 Other*** 856 542 619 Total plan contributions $ 12,442 $ 11,977 $ 11,992 * Pension plans include $0.9 million, $0.8 million and $0.7 million for the years ended 2017, 2016 and 2015, respectively, to multiemployer plans not discussed above. ** Health plans include $1.6 million, $1.6 million and $1.4 million for the years ended 2017, 2016 and 2015, respectively, to multiemployer plans not discussed above. *** Other consists of union costs which were not itemized between pension and health plans. Other includes $0.2 million, $0.2 million and $0.2 million for the years ended 2017, 2016 and 2015, respectively, in connection with other multiemployer plans not discussed above.

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note Disclosure, Disclosure of Compensation Related Costs, Share-based Payments and Earnings Per Share [Abstract]
Schedule of Change in Net Income Attributable to Common Shareholders	The following is net income attributable to common stockholders and the issuance of our class A shares in exchange for the conversion of OP units into common stock (amounts in thousands): Year ended December 31, 2017 2016 2015 Net income attributable to common stockholders $ 62,647 $ 51,456 $ 33,730 Increase in additional paid-in capital for the conversion of OP units into common stock 23,529 24,044 62,003 Change from net income attributable to common stockholders and transfers from noncontrolling interests $ 86,176 $ 75,500 $ 95,733
Dividends Declared	The following table summarizes the dividends paid on our Class A common stock and Class B common stock for the years ended December 31, 2017, 2016 and 2015: Record Date Payment Date Amount per Share December 15, 2017 December 29, 2017 $0.105 September 15, 2017 September 29, 2017 $0.105 June 15, 2017 June 30, 2017 $0.105 March 15, 2017 March 31, 2017 $0.105 December 15, 2016 December 29, 2016 $0.105 September 19, 2016 September 30, 2016 $0.105 June 15, 2016 June 30, 2016 $0.105 March 16, 2016 March 31, 2016 $0.085 December 15, 2015 December 31, 2015 $0.085 September 15, 2015 September 30, 2015 $0.085 June 15, 2015 June 30, 2015 $0.085 March 13, 2015 March 31, 2015 $0.085
Summary of Restricted Stock and Long-Term Incentive Plan Activity	The following is a summary of restricted stock and LTIP unit activity for the year ended December 31, 2017 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2016 107,793 2,881,629 $ 10.01 Vested (48,900 ) (588,367 ) 11.97 Granted 34,407 1,372,574 13.77 Forfeited or unearned (2,509 ) (77,227 ) 5.36 Unvested balance at December 31, 2017 90,791 3,588,609 $ 11.20
Schedule of Earnings Per Share, Basic and Diluted	Earnings per share for the years ended December 31, 2017 , 2016 and 2015 is computed as follows (amounts in thousands, except per share amounts): For the Year Ended December 31, 2017 2016 2015 Numerator - Basic: Net income $ 118,253 $ 107,250 $ 79,928 Private perpetual preferred unit distributions (936 ) (936 ) (936 ) Net income attributable to non-controlling interests (54,670 ) (54,858 ) (45,262 ) Earnings allocated to unvested shares (36 ) (36 ) (24 ) Net income attributable to common stockholders - basic $ 62,611 $ 51,420 $ 33,706 Numerator - Diluted: Net income $ 118,253 $ 107,250 $ 79,928 Private perpetual preferred unit distributions (936 ) (936 ) (936 ) Earnings allocated to unvested shares (36 ) (36 ) (550 ) Net income attributable to common stockholders - diluted $ 117,281 $ 106,278 $ 78,442 Denominator: Weighted average shares outstanding - basic 158,380 133,881 114,245 Operating partnership units 138,075 142,967 151,669 Effect of dilutive securities: Stock-based compensation plans 775 454 707 Exchangeable senior notes 819 266 — Weighted average shares outstanding - diluted 298,049 277,568 266,621 Earnings per share - basic $ 0.40 $ 0.38 $ 0.30 Earnings per share - diluted $ 0.39 $ 0.38 $ 0.29

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	TRS Holdings and Observatory TRS are taxable entities and their consolidated provision for income taxes consisted of the following for the years ended December 31, 2017 , 2016 and 2015 (amounts in thousands): For the Year Ended December 31, 2017 2016 2015 Current: Federal $ (3,923 ) $ (3,632 ) $ (2,714 ) State and local (2,304 ) (2,055 ) (1,502 ) Total current (6,227 ) (5,687 ) (4,216 ) Deferred: Federal (446 ) (291 ) 169 State and local — (168 ) 98 Total deferred (446 ) (459 ) 267 Income tax expense $ (6,673 ) $ (6,146 ) $ (3,949 )
Schedule of Actual Tax Provision Differed From Federal Statutory Corporate Rate	The actual tax provision differed from that computed at the federal statutory corporate rate as follows (amounts in thousands): For the Year Ended December 31, 2017 2016 2015 Federal tax expense at 34% statutory rate $ (4,684 ) $ (4,629 ) $ (3,003 ) State income taxes, net of federal benefit (1,543 ) (1,517 ) (946 ) Corporate income tax rate adjustment (446 ) — — Income tax expense $ (6,673 ) $ (6,146 ) $ (3,949 )
Schedule of Deferred Tax Assets	The income tax effects of temporary differences that give rise to deferred tax assets are presented below as of December 31, 2017 , 2016 and 2015 (amounts in thousands): 2017 2016 2015 Deferred tax assets: Deferred revenue on unredeemed observatory admission ticket sales $ 1,395 $ 198 $ 267

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following tables provide components of segment profit for each segment for the years ended December 31, 2017 , 2016 and 2015, as reviewed by management (amounts in thousands): 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 483,944 $ — $ — $ 483,944 Intercompany rental revenue 77,646 — (77,646 ) — Tenant expense reimbursement 73,679 — — 73,679 Observatory revenue — 127,118 — 127,118 Third-party management and other fees 1,400 — — 1,400 Other revenue and fees 26,327 — — 26,327 Total revenues 662,996 127,118 (77,646 ) 712,468 Operating expenses: Property operating expenses 163,531 — — 163,531 Intercompany rent expense — 77,646 (77,646 ) — Ground rent expense 9,326 — — 9,326 General and administrative expenses 50,315 — — 50,315 Observatory expenses — 30,275 — 30,275 Real estate taxes 102,466 — — 102,466 Depreciation and amortization 160,630 80 — 160,710 Total operating expenses 486,268 108,001 (77,646 ) 516,623 Total operating income 176,728 19,117 — 195,845 Interest expense (68,473 ) — — (68,473 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments (289 ) — — (289 ) Income before income taxes 105,809 19,117 — 124,926 Income tax expense (1,306 ) (5,367 ) — (6,673 ) Net income $ 104,503 $ 13,750 $ — $ 118,253 Segment assets $ 3,670,907 $ 260,440 $ — $ 3,931,347 Expenditures for segment assets $ 191,541 $ 36,621 $ — $ 228,162 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 460,653 $ — $ — $ 460,653 Intercompany rental revenue 75,658 — (75,658 ) — Tenant expense reimbursement 73,459 — — 73,459 Observatory revenue — 124,814 — 124,814 Third-party management and other fees 1,766 — — 1,766 Other revenue and fees 17,293 15 — 17,308 Total revenues 628,829 124,829 (75,658 ) 678,000 Operating expenses: Property operating expenses 153,850 — — 153,850 Intercompany rent expense — 75,658 (75,658 ) — Ground rent expense 9,326 — — 9,326 General and administrative expenses 49,078 — — 49,078 Observatory expenses — 29,833 — 29,833 Real estate taxes 96,061 — — 96,061 Acquisition expenses 98 — — 98 Depreciation and amortization 154,817 394 — 155,211 Total operating expenses 463,230 105,885 (75,658 ) 493,457 Total operating income (loss) 165,599 18,944 — 184,543 Interest expense (70,595 ) — — (70,595 ) Loss on early extinguishment of debt (552 ) — — (552 ) Income before income taxes 94,452 18,944 — 113,396 Income tax expense (1,361 ) (4,785 ) — (6,146 ) Net income $ 93,091 $ 14,159 $ — $ 107,250 Segment assets $ 3,641,844 $ 249,109 $ — $ 3,890,953 Expenditures for segment assets $ 197,680 $ — $ — $ 197,680 2015 Real Estate Observatory Other Intersegment Elimination Total Revenues: Rental revenue $ 447,784 $ — $ — $ — $ 447,784 Intercompany rental revenue 68,255 — — (68,255 ) — Tenant expense reimbursement 79,516 — — — 79,516 Observatory revenue — 112,172 — — 112,172 Construction revenue — — 5,696 (3,715 ) 1,981 Third-party management and other fees 2,133 — — — 2,133 Other revenue and fees 14,048 — — — 14,048 Total revenues 611,736 112,172 5,696 (71,970 ) 657,634 Operating expenses: Property operating expenses 158,638 — — — 158,638 Intercompany rent expense — 68,255 — (68,255 ) — Ground rent expense 9,326 — — — 9,326 General and administrative expenses 38,073 — — — 38,073 Observatory expenses — 32,174 — — 32,174 Construction expenses — — 6,539 (3,317 ) 3,222 Real estate taxes 93,165 — — — 93,165 Acquisition expenses 193 — — — 193 Depreciation and amortization 171,035 338 101 — 171,474 Total operating expenses 470,430 100,767 6,640 (71,572 ) 506,265 Total operating income (loss) 141,306 11,405 (944 ) (398 ) 151,369 Interest expense (65,743 ) — — — (65,743 ) Loss on early extinguishment of debt (1,749 ) — — — (1,749 ) Income (loss) before income taxes 73,814 11,405 (944 ) (398 ) 83,877 Income tax (expense) benefit (1,498 ) (2,791 ) 340 — (3,949 ) Net income $ 72,316 $ 8,614 $ (604 ) $ (398 ) $ 79,928 Segment assets $ 3,058,250 $ 241,511 $ 889 $ — $ 3,300,650 Expenditures for segment assets $ 156,543 $ 211 $ — $ — $ 156,754

Summary of Quarterly Financia33

Summary of Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The quarterly results of operations of our company for the years ended December 31, 2017 , 2016 and 2015 are as follows (amounts in thousands): March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Revenues $ 164,954 $ 177,124 $ 187,320 $ 183,070 Operating income $ 36,666 $ 51,434 $ 56,781 $ 50,964 Net income $ 19,145 $ 31,359 $ 35,489 $ 32,260 Net income attributable to common stockholders $ 9,985 $ 16,584 $ 18,806 $ 17,272 Net income per share attributable to common stockholders: Basic and diluted $ 0.06 $ 0.10 $ 0.12 $ 0.11 March 31, 2016 June 30, 2016 September 30, 2016 December 31, 2016 Revenues $ 157,074 $ 165,815 $ 175,848 $ 179,263 Operating income $ 34,114 $ 44,192 $ 53,586 $ 52,651 Net income $ 16,705 $ 24,640 $ 32,897 $ 33,008 Net income attributable to common stockholders $ 7,428 $ 11,089 $ 15,973 $ 16,966 Net income per share attributable to common stockholders: Basic and diluted $ 0.06 $ 0.09 $ 0.12 $ 0.11 March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 Revenues $ 151,882 $ 164,773 $ 175,779 $ 165,200 Operating income $ 23,757 $ 45,039 $ 45,343 $ 37,230 Net income $ 7,888 $ 26,585 $ 26,085 $ 19,370 Net income attributable to common stockholders $ 3,138 $ 11,120 $ 11,220 $ 8,252 Net income per share attributable to common stockholders: Basic and diluted $ 0.03 $ 0.10 $ 0.10 $ 0.07

Description of Business and O34

Description of Business and Organization - Narrative (Details)	12 Months Ended
	Dec. 31, 2017ft²entityparceloffice_and_property
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	10,100,000
OP units owned by the Company, percent	53.80%
Number of entities to be treated as taxable REIT subsidiary | entity	2
Office Building [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	9,400,000
Number of offices and properties (property) | office_and_property	14
Office Building [Member] | Manhattan [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	7,600,000
Number of offices and properties (property) | office_and_property	9
Office Building [Member] | Fairfield County, Connecticut and Westchester County, New York [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	1,900,000
Number of offices and properties (property) | office_and_property	5
Development Parcel [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of offices and properties (property) | parcel	3
Retail [Member] | Manhattan and Westport, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	205,740
Retail [Member] | Manhattan [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	507,395
Number of offices and properties (property) | office_and_property	4
Retail [Member] | Westport, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of offices and properties (property) | office_and_property	2
Other Property [Member] | Stamford, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in sqft)	380,000

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounting Policies [Line Items]
Lease cancellation fees	$ 13,600,000	$ 7,700,000	$ 2,000,000
Deferred revenue	4,100,000	4,100,000
Advertising and marketing expense	7,600,000	9,400,000	8,700,000
Interest costs capitalized	$ 500,000	$ 0	$ 0
Number of reportable segments (segment) | segment	2
Remaining contractual payments under ground lease agreements	$ 61,284,000
Capitalized internal leasing costs	$ 2,600,000
Building and Building Improvements [Member]
Accounting Policies [Line Items]
Useful life	39 years
Corporate Equipment [Member] | Minimum [Member]
Accounting Policies [Line Items]
Useful life	3 years
Corporate Equipment [Member] | Maximum [Member]
Accounting Policies [Line Items]
Useful life	7 years

Deferred Costs, Acquired Leas36

Deferred Costs, Acquired Lease Intangibles and Goodwill - Schedule of Deferred Costs, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs [Line Items]
Leasing costs	$ 164,751	$ 140,325
Total deferred costs, gross amount	469,530	468,208
Less: accumulated amortization	(215,102)	(195,617)
Total deferred costs, net, excluding net deferred financing costs	254,428	272,591
Acquired in-place lease value and deferred leasing costs [Member]
Deferred Costs [Line Items]
Acquired finite-lived intangible assets, gross	237,364	253,113
Acquired above-market leases [Member]
Deferred Costs [Line Items]
Acquired finite-lived intangible assets, gross	$ 67,415	$ 74,770

Deferred Costs, Acquired Leas37

Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Deferred Costs [Line Items]
Amortization of deferred leasing and acquired deferred leasing costs	$ 24,100	$ 24,200	$ 25,400
Amortization of acquired above and below-market leases, net	5,721	8,795	19,353
Goodwill	491,479	491,479
Empire State Building observatory operations [Member]
Deferred Costs [Line Items]
Goodwill				$ 227,500
Empire State Building [Member]
Deferred Costs [Line Items]
Goodwill				250,800
501 Seventh Avenue [Member]
Deferred Costs [Line Items]
Goodwill				$ 13,200
Lease agreements [Member]
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	$ 17,100	24,600	$ 37,700
Ground lease [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	25 years
In-place leases and deferred leasing costs [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	4 years 10 months
Above-market leases [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	3 years 10 months 24 days
Below-market Lease [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	4 years 2 months
Unsecured revolving credit facility [Member] | Revolving Credit Facility [Member]
Deferred Costs [Line Items]
Net deferred financing costs	$ 8,300	$ 4,500

Deferred Costs, Acquired Leas38

Deferred Costs, Acquired Lease Intangibles and Goodwill - Acquired Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Acquired below-market ground leases	$ 396,916	$ 396,916
Less: accumulated amortization	(28,687)	(20,856)
Acquired below-market ground leases, net	368,229	376,060
Acquired below-market leases	(132,026)	(135,026)
Less: accumulated amortization	65,979	52,726
Acquired below-market leases, net	$ (66,047)	$ (82,300)

Deferred Costs, Acquired Leas39

Deferred Costs, Acquired Lease Intangibles and Goodwill - Future Amortization Expense and Rental Revenue (Details) $ in Thousands	Dec. 31, 2017USD ($)
Future Rental Revenue [Abstract]
2,018	$ 6,442
2,019	6,689
2,020	3,559
2,021	2,857
2,022	3,175
Thereafter	12,690
Future Rental Revenue	35,412
Ground lease [Member]
Future Amortization Expense [Abstract]
2,018	7,831
2,019	7,831
2,020	7,831
2,021	7,831
2,022	7,831
Thereafter	329,074
Future Amortization Expense	368,229
Lease agreements [Member]
Future Amortization Expense [Abstract]
2,018	18,650
2,019	15,996
2,020	13,046
2,021	11,302
2,022	10,485
Thereafter	41,549
Future Amortization Expense	$ 111,028

Debt - Schedule of Long term D

Debt - Schedule of Long term Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018	Jan. 31, 2018	Aug. 31, 2017	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017	Dec. 31, 2016	Aug. 31, 2014
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 0							$ 0
Deferred financing costs, net	(17,407,000)							(10,904,000)
Total	717,164,000							759,016,000
Mortgages [Member]
Debt Instrument [Line Items]
Fixed rate debt	721,224,000							752,840,000
Total principal	1,701,224,000							1,617,840,000
Unamortized (discount) premiums, net of unamortized premiums (discount)	(3,370,000)							905,000
Deferred financing costs, net	(9,133,000)							(6,414,000)
Total	1,688,721,000							1,612,331,000
Mortgages [Member] | 1333 Broadway [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 66,602,000							67,656,000
Stated Rate	6.32%
Effective rate	3.73%
Mortgages [Member] | 1400 Broadway - First Lien [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 66,632,000							67,714,000
Stated Rate	6.12%
Effective rate	3.37%
Mortgages [Member] | 1400 Broadway - Second Lien [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 9,172,000							9,389,000
Stated Rate	3.35%
Effective rate	3.36%
Mortgages [Member] | 111 West 33rd Street - First Lien [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 74,045,000							75,261,000
Stated Rate	6.01%
Effective rate	3.34%
Mortgages [Member] | 111 West 33rd Street - Second Lien [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 9,369,000							9,509,000
Stated Rate	6.56%
Effective rate	3.64%
Mortgages [Member] | 1350 Broadway [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 37,144,000							37,764,000
Stated Rate	5.87%
Effective rate	3.71%
Mortgages [Member] | Metro Center [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 93,948,000							95,985,000
Stated Rate	3.59%
Effective rate	3.67%
Mortgages [Member] | 10 Union Square [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 50,000,000							50,000,000
Stated Rate	3.70%
Effective rate	3.97%
Mortgages [Member] | 10 Bank Street [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 34,602,000							31,544,000
Stated Rate	4.23%					4.23%
Effective rate	4.49%
Face amount						$ 35,000,000
Mortgages [Member] | 1542 Third Avenue [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 30,000,000							17,795,000
Stated Rate	4.29%						4.29%
Effective rate	4.64%
Face amount							$ 30,000,000
Mortgages [Member] | First Stamford Place [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 180,000,000							235,067,000
Stated Rate	4.28%				4.28%
Effective rate	4.60%
Face amount					$ 180,000,000
Mortgages [Member] | First Stamford Place - First Lien [Member]
Debt Instrument [Line Items]
Stated Rate	4.09%				4.09%
Face amount	$ 164,000,000				$ 164,000,000
Mortgages [Member] | First Stamford Place - Second Lien [Member]
Debt Instrument [Line Items]
Stated Rate	6.25%				6.25%
Face amount	$ 16,000,000				$ 16,000,000
Mortgages [Member] | 1010 Third Avenue and 77 West 55th Street [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 39,710,000							26,502,000
Stated Rate	4.01%				4.01%
Effective rate	4.39%
Face amount					$ 40,000,000
Mortgages [Member] | 383 Main Avenue [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 30,000,000							28,654,000
Stated Rate	4.44%				4.44%
Effective rate	4.72%
Face amount					$ 30,000,000
Convertible debt [Member] | Exchangeable Senior Notes due August 15, 2019 [Member]
Debt Instrument [Line Items]
Fixed rate debt	$ 250,000,000							250,000,000
Stated Rate	2.625%								2.625%
Effective rate	3.93%								3.80%
Face amount									$ 250,000,000
Senior Notes [Member] | Series A Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Total	$ 100,000,000							100,000,000
Stated Rate	3.93%
Effective rate	3.98%
Senior Notes [Member] | Series B Senior Notes due 2027 [Member]
Debt Instrument [Line Items]
Total	$ 125,000,000							125,000,000
Stated Rate	4.09%
Effective rate	4.14%
Senior Notes [Member] | Series C Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Total	$ 125,000,000							125,000,000
Stated Rate	4.18%
Effective rate	4.23%
Senior Notes [Member] | Series D Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Total	$ 115,000,000							0
Stated Rate	4.08%
Effective rate	4.08%
Face amount	$ 115,000,000
Senior Notes [Member] | Series E Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Total	$ 0							0
Stated Rate	4.26%
Effective rate	0.00%
Face amount	$ 160,000,000
Senior Notes [Member] | Series F Senior Notes due 2033 [Member]
Debt Instrument [Line Items]
Total	$ 0							0
Stated Rate	4.44%
Effective rate	0.00%
Face amount	$ 175,000,000
Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 0							0
Effective rate	2.66%
Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.10%
Revolving Credit Facility [Member] | Unsecured Term Loan Facility [Member]
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 265,000,000			$ 265,000,000				$ 265,000,000
Effective rate	2.1485%
Pay rate	3.35%
Revolving Credit Facility [Member] | Unsecured Term Loan Facility [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%
Subsequent Event [Member] | Mortgages [Member] | 1333 Broadway [Member]
Debt Instrument [Line Items]
Stated Rate			4.21%
Face amount			$ 160,000,000
Scenario, Forecast [Member] | Subsequent Event [Member] | Senior Notes [Member] | Series E Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Face amount		$ 160,000,000
Scenario, Forecast [Member] | Subsequent Event [Member] | Senior Notes [Member] | Series F Senior Notes due 2033 [Member]
Debt Instrument [Line Items]
Face amount		$ 175,000,000

Debt - Mortgage Debt (Details)

Debt - Mortgage Debt (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017
Debt Instrument [Line Items]
Repayments of mortgage loan		$ 346,615,000	$ 32,305,000	$ 146,918,000
Mortgages [Member]
Debt Instrument [Line Items]
Fixed rate debt		$ 721,224,000	752,840,000
Mortgages [Member] | 1542 Third Avenue [Member]
Debt Instrument [Line Items]
Face amount							$ 30,000,000
Stated interest rate		4.29%					4.29%
Fixed rate debt		$ 30,000,000	17,795,000
Mortgages [Member] | 10 Bank Street [Member]
Debt Instrument [Line Items]
Face amount						$ 35,000,000
Stated interest rate		4.23%				4.23%
Fixed rate debt		$ 34,602,000	31,544,000
Mortgages [Member] | First Stamford Place [Member]
Debt Instrument [Line Items]
Face amount					$ 180,000,000
Stated interest rate		4.28%			4.28%
Fixed rate debt		$ 180,000,000	235,067,000
Mortgages [Member] | First Stamford Place - First Lien [Member]
Debt Instrument [Line Items]
Face amount		$ 164,000,000			$ 164,000,000
Stated interest rate		4.09%			4.09%
Mortgages [Member] | First Stamford Place - Second Lien [Member]
Debt Instrument [Line Items]
Face amount		$ 16,000,000			$ 16,000,000
Stated interest rate		6.25%			6.25%
Mortgages [Member] | 1010 Third Avenue and 77 West 55th Street [Member]
Debt Instrument [Line Items]
Face amount					$ 40,000,000
Stated interest rate		4.01%			4.01%
Fixed rate debt		$ 39,710,000	26,502,000
Mortgages [Member] | 383 Main Avenue [Member]
Debt Instrument [Line Items]
Face amount					$ 30,000,000
Stated interest rate		4.44%			4.44%
Fixed rate debt		$ 30,000,000	28,654,000
Mortgages [Member] | 1333 Broadway [Member]
Debt Instrument [Line Items]
Stated interest rate		6.32%
Fixed rate debt		$ 66,602,000	$ 67,656,000
Subsequent Event [Member] | Mortgages [Member] | 1333 Broadway [Member]
Debt Instrument [Line Items]
Face amount	$ 160,000,000
Stated interest rate	4.21%
Subsequent Event [Member] | Mortgages [Member] | 1400 Broadway [Member]
Debt Instrument [Line Items]
Repayments of mortgage loan	$ 75,800,000

Debt - Schedule of Maturities

Debt - Schedule of Maturities of Long-term Debt (Details) - Mortgages [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
2018 Amortization	$ 4,417
2019 Amortization	3,790
2020 Amortization	3,938
2021 Amortization	4,090
2022 Amortization	5,455
Thereafter	37,890
Total Amortization	59,580
2018 Maturities	262,195
2019 Maturities	250,000
2020 Maturities	0
2021 Maturities	0
2022 Maturities	265,000
Thereafter	864,449
Total Maturities	1,641,644
2,018	266,612
2,019	253,790
2,020	3,938
2,021	4,090
2,022	270,455
Thereafter	902,339
Total	$ 1,701,224	$ 1,617,840

Debt - Deferred Financing Cost

Debt - Deferred Financing Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Financing costs	$ 24,446	$ 23,145
Less: accumulated amortization	(7,039)	(12,241)
Total deferred financing costs, net	17,407	10,904
Amortization of financing costs	4,700	5,000	$ 6,100
Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Net deferred financing costs	$ 8,300	$ 4,500

Debt - Unsecured Revolving Cre

Debt - Unsecured Revolving Credit and Term Loan Facility (Details)	1 Months Ended	12 Months Ended
	Aug. 31, 2017USD ($)option	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Loss on early extinguishment of debt		$ 2,157,000	$ 552,000	$ 1,749,000
Unsecured revolving credit facility		0	0
Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Loss on early extinguishment of debt		2,200,000
Current borrowing capacity	$ 1,100,000,000
Unsecured revolving credit facility		0	0
Option to extend maturity, number | option	2
Extension period	6 months
Maximum leverage ratio	60.00%
Maximum consolidated secured indebtedness to asset value	40.00%
Minimum tangible net worth	$ 1,200,000,000
Tangible net worth, minimum percent of net equity proceeds received	75.00%
Minimum adjusted EBITDA to consolidated fixed charges	1.50
Minimum net operating income to unsecured debt	1.75
Maximum ratio of unsecured debt to unencumbered asset value	60.00%
Revolving Credit Facility [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Current borrowing capacity	$ 265,000,000
Unsecured revolving credit facility	265,000,000	$ 265,000,000	$ 265,000,000
Revolving Credit Facility [Member] | Unsecured Revolving Credit Facility And Term Loan [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	1,365,000,000
Credit facility higher borrowing capacity option	$ 1,750,000,000
Minimum [Member] | Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Extension fee percent of outstanding commitments under revolving credit facility	0.0625%
Maximum [Member] | Revolving Credit Facility [Member] | Unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Extension fee percent of outstanding commitments under revolving credit facility	0.075%

Debt - Senior Unsecured Notes

Debt - Senior Unsecured Notes Exchangeable (Details)	1 Months Ended	12 Months Ended
	Aug. 31, 2014USD ($)d$ / shares	Dec. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Senior unsecured notes, net		$ 707,895,000	$ 590,388,000
Interest expense		68,473,000	70,595,000	$ 65,743,000
Amortization expense of deferred financing costs		$ 4,700,000	5,000,000	6,100,000
Convertible debt [Member] | Exchangeable Senior Notes due August 15, 2019 [Member]
Debt Instrument [Line Items]
Face amount	$ 250,000,000
Stated interest rate	2.625%	2.625%
Conversion price (USD per share) | $ / shares	$ 19.45	$ 19.32
Debt, conversion ratio	0.0514059	0.0517605
Percentage of principal redeemed	100.00%
Effective rate	3.80%	3.93%
Senior unsecured notes, net	$ 236,600,000
Embedded conversion option		$ 13,400,000	13,400,000
Remaining discount amortization period	5 years
Unamortized discount		4,300,000	7,000,000
Underwriting expense	$ 3,100,000
Deferred finance costs	$ 2,900,000
Embedded conversion feature, reduction		200,000	200,000
Interest on note		9,900,000	9,900,000	9,900,000
Interest expense		6,600,000	6,600,000	6,600,000
Accretion of debt discount		2,700,000	2,700,000	2,700,000
Amortization expense of deferred financing costs		$ 600,000	$ 600,000	$ 600,000
Covenant scenario one [Member] | Convertible debt [Member] | Exchangeable Senior Notes due August 15, 2019 [Member]
Debt Instrument [Line Items]
Threshold percentage of stock price trigger	130.00%
Threshold trading days | d	20
Threshold consecutive trading days | d	30
Covenant scenario two [Member] | Convertible debt [Member] | Exchangeable Senior Notes due August 15, 2019 [Member]
Debt Instrument [Line Items]
Threshold percentage of stock price trigger	98.00%
Threshold consecutive trading days | d	5
Threshold consecutive business days	5 days

Debt - Senior Unsecured Note46

Debt - Senior Unsecured Notes (Details) - Senior Notes [Member]	Dec. 31, 2017USD ($)
Series D, Series E, and Series F Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Face amount	$ 450,000,000
Series D Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Face amount	$ 115,000,000
Stated interest rate	4.08%
Series E Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Face amount	$ 160,000,000
Stated interest rate	4.26%
Series F Senior Notes due 2033 [Member]
Debt Instrument [Line Items]
Face amount	$ 175,000,000
Stated interest rate	4.44%

Accounts Payable and Accrued 47

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued capital expenditures	$ 71,769	$ 66,620
Accounts payable and accrued expenses	32,509	36,246
Payable to the estate of Leona M. Helmsley	0	18,367
Interest rate swap agreements liability	436	5,591
Accrued interest payable	5,687	6,230
Due to affiliated companies	448	1,010
Total accounts payable and accrued expenses	$ 110,849	$ 134,064

Financial Instruments and Fai48

Financial Instruments and Fair Values - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Interest rate swap agreements liability	$ 436	$ 5,591
Unrealized loss on valuation of interest rate swap agreements	11,658	3,054	$ 1,922
Interest rate swaps [Member]
Derivative [Line Items]
Interest rate swap agreements liability	500
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Unrealized loss on valuation of interest rate swap agreements	10,500	3,100
Loss expected to be reclassified within twelve months	1,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Notional amount	265,000	890,000
Prepaid expenses and other assets [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Interest rate swap agreements asset	600
Accounts payable and accrued expenses [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Interest rate swap agreements liability	$ 400	$ 5,600

Financial Instruments and Fai49

Financial Instruments and Fair Values - Terms of Agreements and Fair Value (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2017
Derivatives, Fair Value [Line Items]
Reclassification into earnings as an increase to interest expense	$ 1,500,000
Term of reclassification	10 years
Loss from derivative financial instruments	$ 289,000	$ 0	$ 0
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset	0	614,000
Liability	(436,000)	(5,591,000)
Interest Rate Swap, One Month LIBOR, 2.1485% [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 265,000,000
Pay Rate	2.1485%
Asset	$ 0	0
Liability	(436,000)	(1,634,000)
Interest Rate Swap, Three Month LIBOR, 2.5050% [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000
Pay Rate	2.505%
Asset	$ 0	0
Liability	0	(684,000)
Interest Rate Swap, Three Month LIBOR, 2.5050%, 2 [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 80,000,000			$ 100,000,000
Pay Rate	2.505%
Asset	$ 0	0
Liability	0	(685,000)
Notional amount, terminated				$ 20,000,000
Interest Rate Swap, Three Month LIBOR, 2.4860% [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000
Pay Rate	2.486%
Asset	$ 0	224,000
Liability	0	0
Interest Rate Swap, Three Month LIBOR, 2.4860%, 2 [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000
Pay Rate	2.486%
Asset	$ 0	223,000
Liability	0	0
Interest Rate Swap, Three Month LIBOR, 2.4860%, 3 [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000
Pay Rate	2.486%
Asset	$ 0	167,000
Liability	0	0
Interest Rate Swap, Three Month LIBOR, 2.7620% [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000
Pay Rate	2.762%
Asset	$ 0	0
Liability	0	(1,295,000)
Interest Rate Swap, Three Month LIBOR, 2.7620%, 2 [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000
Pay Rate	2.762%
Asset	$ 0	0
Liability	0	(1,293,000)
Two Interest Rate Swaps, Three Month LIBOR, 2.5050% [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Deferred losses on terminated hedges	15,100,000
Other Nonoperating Income (Expense) [Member] | Interest Rate Swap, Three Month LIBOR, 2.5050%, 2 [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | LIBOR [Member]
Derivatives, Fair Value [Line Items]
Loss from derivative financial instruments	$ 300,000	$ 0	$ 0

Financial Instruments and Fai50

Financial Instruments and Fair Values - Gain and Loss of Cash Flow Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ 68,473	$ 70,595	$ 65,743
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income (loss)	(11,658)	(3,054)	(1,922)
Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense	(1,142)	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ 1,142	$ 0	$ 0

Financial Instruments and Fai51

Financial Instruments and Fair Values - Schedule of the aggregate carrying value of debt and estimates of fair value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	$ 436	$ 5,591
Carrying Amount [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	263,662	262,927
Carrying Amount [Member] | Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	717,164	759,016
Carrying Amount [Member] | Exchangeable notes [Member] | Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	244,739	241,474
Carrying Amount [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	463,156	348,914
Fair Value [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Fair Value [Member] | Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	707,300	755,640
Fair Value [Member] | Exchangeable notes [Member] | Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	275,723	282,435
Fair Value [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	460,352	339,274
Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | Exchangeable notes [Member] | Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Exchangeable notes [Member] | Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	275,723	282,435
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	707,300	755,640
Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Exchangeable notes [Member] | Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	460,352	339,274
Interest rate swaps [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	500
Interest rate swaps [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	436	5,591
Interest rate swaps [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	436	5,591
Interest rate swaps [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	0	0
Interest rate swaps [Member] | Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	436	5,591
Interest rate swaps [Member] | Fair Value [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	$ 0	$ 0

Rental Income (Details)

Rental Income (Details)	12 Months Ended
	Dec. 31, 2017
Minimum [Member]
Operating Leases [Line Items]
Term of lease	1 year
Maximum [Member]
Operating Leases [Line Items]
Term of lease	21 years

Rental Income - Schedule of Fu

Rental Income - Schedule of Future Minimum Payments Receivable for Operating Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Receivable [Abstract]
2,018	$ 463,110
2,019	451,161
2,020	413,745
2,021	381,394
2,022	351,431
Thereafter	1,649,567
Total Future Minimum Payments Receivable for Operating Leases	$ 3,710,408

Commitments and Contingencies

Commitments and Contingencies - Litigation (Details)	Oct. 14, 2014participant
Predecessor [Member] | New York State Supreme Court, New York County [Member]
Loss Contingencies [Line Items]
Number of plaintiffs opting out of settlement (participant)	12

Commitments and Contingencies55

Commitments and Contingencies - Ground Lease Commitments (Details) $ in Thousands	Dec. 31, 2017USD ($)property
Commitments and Contingencies Disclosure [Abstract]
Number of properties subject to ground leases (property) | property	3
2,018	$ 1,518
2,019	1,518
2,020	1,518
2,021	1,518
2,022	1,518
Thereafter	53,694
Total	$ 61,284

Commitments and Contingencies56

Commitments and Contingencies - Unfunded Capital Expenditures (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Unfunded capital expenditures	$ 78.2

Commitments and Contingencies57

Commitments and Contingencies - Major Customers and Other Concentrations (Details) - Customer concentration risk [Member] - Rental revenue [Member]	12 Months Ended
	Dec. 31, 2017office_and_propertytenant	Dec. 31, 2016office_and_propertytenant	Dec. 31, 2015office_and_propertytenant
Concentration Risk [Line Items]
Number of tenants | tenant	5	5	3
Number of properties (property) | office_and_property	6	6	6
Empire State Building Co. [Member]
Concentration Risk [Line Items]
Concentration risk percentage	32.00%	32.60%	31.40%
One Grand Central Place [Member]
Concentration Risk [Line Items]
Concentration risk percentage	13.10%	12.50%	12.20%
111 West 33rd Street [Member]
Concentration Risk [Line Items]
Concentration risk percentage	8.60%	6.80%	8.30%
1400 Broadway [Member]
Concentration Risk [Line Items]
Concentration risk percentage	7.40%	7.80%	7.70%
First Stamford Place [Member]
Concentration Risk [Line Items]
Concentration risk percentage	5.40%	6.40%	6.50%
250 West 57th Street [Member]
Concentration Risk [Line Items]
Concentration risk percentage	5.20%	5.30%	4.80%
Customer 1 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	6.30%	6.40%	6.70%
Customer 2 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	3.20%	3.30%	3.50%
Customer 3 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	2.90%	2.90%	2.00%
Customer 4 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	2.10%	2.30%
Customer 5 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	2.00%	2.00%

Commitments and Contingencies58

Commitments and Contingencies - Multiemployer Pension and Defined Contribution Plans Narrative (Details) - Building Service 32BJ [Member] - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Pension Plans [Member]
Multiemployer Plans [Line Items]
Plan contributions	$ 257.8	$ 249.5	$ 242.3
Health Plans [Member]
Multiemployer Plans [Line Items]
Plan contributions	$ 1,300	$ 1,200	$ 1,100

Commitments and Contingencies59

Commitments and Contingencies - Schedule of Contributions made to Multiemployer Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Multiemployer Plans [Line Items]
Contributions	$ 12,442	$ 11,977	$ 11,992
Pension Plans [Member]
Multiemployer Plans [Line Items]
Contributions	3,035	3,155	3,077
Pension Plans [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	900	800	700
Health Plans [Member]
Multiemployer Plans [Line Items]
Contributions	8,551	8,280	8,296
Health Plans [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	1,600	1,600	1,400
Other [Member]
Multiemployer Plans [Line Items]
Contributions	856	542	619
Other [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	$ 200	$ 200	$ 200

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 29, 2016	Sep. 30, 2016	Aug. 23, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Gross proceeds from sale of shares							$ 621,800							$ 0	$ 611,206	$ 0
Percentage of dividends on common stock received until performance criteria met for LTIP units														10.00%	10.00%
Percentage of dividends on common stock received after performance criteria met for LTIP units														90.00%	90.00%
Percentage of dividends on common stock received in periods after performance criteria met for LTIP units														100.00%	100.00%
Shares and Units [Abstract]
Net income attributable to common stockholders														$ 62,647	$ 51,456	33,730
Increase in additional paid-in capital for the conversion of OP units into common stock														0	0	0
Change from net income attributable to common stockholders and transfers from noncontrolling interests														$ 86,176	$ 75,500	$ 95,733
OP units outstanding (shares)														300,400,000
OP units owned by the Company (shares)														161,500,000
OP units owned by the Company, percent														53.80%
OP units not owned by the Company (shares)														138,900,000
OP units not owned by the Company, percent														46.20%
Private perpetual preferred units, liquidation preference per share (in dollars per share)														$ 16.62	$ 16.62
Dividends (USD per share)														$ 0.42	$ 0.40	$ 0.34
Dividends and Distributions [Abstract]
Partial dividend paid, per common share (USD per share)	$ 0.105	$ 0.105	$ 0.105	$ 0.105	$ 0.105	$ 0.105		$ 0.105	$ 0.085	$ 0.085	$ 0.085	$ 0.085	$ 0.085
Payments of ordinary dividends, common stock														$ 66,800	$ 55,800	$ 39,200
Distributions paid to OP unitholders														59,200	58,200	51,800
Private perpetual preferred unit distributions														$ 936	$ 936	936
Dividends paid, percent taxable as ordinary dividends														100.00%
Private Perpetual Preferred Units [Member]
Shares and Units [Abstract]
Private perpetual preferred units (shares)														1,560,360
Private perpetual preferred units, liquidation preference per share (in dollars per share)														$ 16.62
Dividends (USD per share)														$ 0.60
Common shares [Member] | Common Class A [Member]
Class of Stock [Line Items]
Issuance of common shares (in shares)							29,610,854								29,610,854
Common shares issued (USD per share)							$ 21
Shares and Units [Abstract]
Increase in additional paid-in capital for the conversion of OP units into common stock														$ 57	$ 62	129
Additional Paid-in Capital [Member]
Shares and Units [Abstract]
Increase in additional paid-in capital for the conversion of OP units into common stock														$ 23,529	$ 24,044	$ 62,003
Q REIT Holding LLC [Member]
Class of Stock [Line Items]
Interest held by Q REIT Holding LLC							9.90%
Q REIT Holding LLC [Member] | Common shares [Member] | Common Class A [Member]
Class of Stock [Line Items]
Interest held by Q REIT Holding LLC							19.40%

Equity - Incentive and Share-b

Equity - Incentive and Share-based Compensation (Details) $ / shares in Units, $ in Millions	1 Months Ended				12 Months Ended
	May 31, 2017USD ($)shares	Mar. 31, 2017USD ($)vesting_installmentshares	Jun. 30, 2016USD ($)shares	Feb. 29, 2016USD ($)vesting_installmentshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility rate look-back period					6 years
Period of service, upon completion of which, grantee's LTIP unit and restricted stock awards will immediately vest					10 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unvested beginning balance, per share (USD per share) | $ / shares					$ 10.01
Vested, weighted average grant price, per share (USD per share) | $ / shares					11.97
Granted, weighted average grant price, per share (USD per share) | $ / shares					13.77
Forfeited or unearned, weighted average grant price, per share (USD per share) | $ / shares					5.36
Unvested ending balance, per share (USD per share) | $ / shares					$ 11.20	$ 10.01
Age of grantee at which LTIP unit and restricted stock awards immediately vest					60 years
Long-Term Incentive Plan Unit and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $					$ 19.4	$ 18.4	$ 6.6
Expected term					2 years 9 months 18 days
Risk-free interest rate					1.55%
Expected price volatility					20.00%
Share-based compensation arrangement by share-based payment award, fair value assumptions, expected dividend rate					2.05%	2.10%	1.90%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted, weighted average grant price, per share (USD per share) | $ / shares					$ 13.77	$ 9.60	$ 13.36
Long-Term Incentive Plan Unit and Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term							3 years
Risk-free interest rate							1.00%
Expected price volatility							29.00%
Long-Term Incentive Plan Unit and Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term						2 years 9 months 12 days	2 years 10 months 24 days
Risk-free interest rate						0.84%	0.80%
Expected price volatility						24.00%	24.00%
Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $		$ 1.6		$ 1.4		$ 0.1
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)		47,993		47,168
Performance Based Long-Term Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $		$ 1		$ 0.8
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)		95,156		112,925
Time Restricted Shares [Member]
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)		34,407		44,198
Restricted Stock [Member]
Restricted Stock and LTIP Unit Activity [Roll Forward]
Unvested beginning balance (in shares)					107,793
Vested (in shares)					(48,900)
Granted (in shares)					34,407
Forfeited or unearned (in shares)					(2,509)
Unvested ending balance (in shares)					90,791	107,793
Long-Term Incentive Plan Unit [Member]
Restricted Stock and LTIP Unit Activity [Roll Forward]
Unvested beginning balance (in shares)					2,881,629
Vested (in shares)					(588,367)
Granted (in shares)					1,372,574
Forfeited or unearned (in shares)					(77,227)
Unvested ending balance (in shares)					3,588,609	2,881,629
Long-Term Incentive Plan Units and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value vested in period | $					$ 7.6	$ 5.1	$ 3.5
Awards that Meet Age and Service Requirements for Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Noncash share-based compensation expense recognized | $					1	0.7	0.5
Unrecognized compensation expense | $					$ 0.8
Unrecognized compensation expense, period for recognition (in years)					1 year 13 months 36 days
Awards that Do Not Meet Age and Service Requirements for Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Noncash share-based compensation expense recognized | $					$ 13.1	$ 9	$ 5
Unrecognized compensation expense | $					$ 23.2
Unrecognized compensation expense, period for recognition (in years)					2 years 4 months 6 days
Director [Member] | 2013 Plan Units Granted In May 2017 [Member] | Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $	$ 1
Award vesting period	3 years
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)	50,408
Director [Member] | 2013 Plan Units Vesting June 2019 [Member] | Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $			$ 0.8
Award vesting period			3 years
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)			43,257
Executive Officer [Member] | 2013 Plan Units, Granted in March 2017 [Member] | Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $		$ 6.1
Award vesting period		4 years
Number of vesting installments (vesting_installment) | vesting_installment		3
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)		313,275
Executive Officer [Member] | 2013 Plan Units, Granted in March 2017 [Member] | Performance Based Long-Term Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $		$ 9.6
Award vesting period		3 years
Number of vesting installments (vesting_installment) | vesting_installment		2
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)		865,742
Executive Officer [Member] | 2013 Plan Units Vesting February 2020 [Member] | Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $				$ 5.6
Award vesting period				4 years
Number of vesting installments (vesting_installment) | vesting_installment				3
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)				368,225
Executive Officer [Member] | 2013 Plan Units Vesting February 2020 [Member] | Performance Based Long-Term Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $				$ 8.8
Award vesting period				3 years
Number of vesting installments (vesting_installment) | vesting_installment				2
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)				1,230,228
Executive Officer [Member] | 2013 Plan Units Vesting February 2021 [Member] | Time Based Long-Tern Incentive Plan Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $				$ 1
Award vesting percentage after three years				30.00%
Award vesting percentage after four years				30.00%
Award vesting percentage after five years				40.00%
Restricted Stock and LTIP Unit Activity [Roll Forward]
Granted (in shares)				62,814
2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under the plan (shares)					12,200,000
Number of shares that remain available for future issuance (shares)					7,000,000

Equity - Earnings Per Share (D

Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income	$ 32,260	$ 35,489	$ 31,359	$ 19,145	$ 33,008	$ 32,897	$ 24,640	$ 16,705	$ 19,370	$ 26,085	$ 26,585	$ 7,888	$ 118,253	$ 107,250	$ 79,928
Private perpetual preferred unit distributions													(936)	(936)	(936)
Net income attributable to non-controlling interests													(54,670)	(54,858)	(45,262)
Earnings allocated to unvested shares													(36)	(36)	(24)
Net income attributable to common stockholders - basic													62,611	51,420	33,706
Earnings allocated to unvested shares													(36)	(36)	(550)
Net income attributable to common stockholders - diluted													$ 117,281	$ 106,278	$ 78,442
Denominator:
Weighted average shares outstanding - basic (shares)													158,380,000	133,881,000	114,245,000
Operating partnership units (shares)													138,075,000	142,967,000	151,669,000
Effect of dilutive securities, stock-based compensation plans (shares)													775,000	454,000	707,000
Effect of dilutive securities, exchangeable senior notes (shares)													819,000	266,000	0
Weighted average shares outstanding - dilutive (in shares)													298,049,000	277,568,000	266,621,000
Basic (USD per share)													$ 0.40	$ 0.38	$ 0.30
Diluted (USD per share)													$ 0.39	$ 0.38	$ 0.29
Antidilutive securities (shares)													834,267	800,746	0

Related Party Transactions - Q

Related Party Transactions - QIA (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 23, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Gross proceeds from sale of shares	$ 621,800	$ 0	$ 611,206	$ 0
Common Class A [Member]
Noncontrolling Interest [Line Items]
Common stock, par value (USD per share)		$ 0.01	$ 0.01
Common shares [Member] | Common Class A [Member]
Noncontrolling Interest [Line Items]
Issuance of common shares (in shares)	29,610,854		29,610,854
Common shares issued (USD per share)	$ 21
Q REIT Holding LLC [Member]
Noncontrolling Interest [Line Items]
Interest held by Q REIT Holding LLC	9.90%
Minimum interest required to be held by affiliate of QIA in order to purchase new equity securities	5.00%
Threshold of equity securities issuance where top up rights are exercisable	$ 1,000
Threshold to indemnify	10.00%
Q REIT Holding LLC [Member] | Common shares [Member] | Common Class A [Member]
Noncontrolling Interest [Line Items]
Interest held by Q REIT Holding LLC	19.40%

Related Party Transactions - T

Related Party Transactions - Tax Protection Agreement (Details) - Affiliated Entity [Member] $ in Millions	Oct. 07, 2013USD ($)property
Related Party Transaction [Line Items]
Number of properties protected (property) | property	4
Aggregate number of operating partnership units and common stock threshold during tax protection period	50.00%
Bottom dollar guarantee of aggregate indebtedness during tax protection period | $	$ 160

Related Party Transactions - E

Related Party Transactions - Excluded Properties and Businesses (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)office_and_propertyinterestproperty	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Retail [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties (property) | office_and_property	4
Office Building [Member]
Related Party Transaction [Line Items]
Number of properties (property) | office_and_property	14
Office Building [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties (property) | office_and_property	9
Malkin Group [Member] | Mezzanine and Senior Equity Funds [Member]
Related Party Transaction [Line Items]
Number of interests owned (interest) | interest	2
Malkin Group [Member] | Residential Property Manager [Member]
Related Party Transaction [Line Items]
Number of properties (property) | interest	5
Number of interests owned (interest) | interest	5
Malkin Group [Member] | Multi-family Property [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties (property)	7
Malkin Group [Member] | Retail [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties (property)	5
Malkin Group [Member] | Retail [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties (property)	2
Malkin Group [Member] | Former Post Office [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties (property)	1
Malkin Group [Member] | Office Building [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties (property)	1
Supervisory fee revenue [Member] | Third party management and other fees [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenue from related parties | $	$ 1.1	$ 1.4	$ 1.8
Property management fee revenue [Member] | Third party management and other fees [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenue from related parties | $	$ 0.3	$ 0.4	$ 0.3

Related Party Transactions - R

Related Party Transactions - Registration Rights (Details) - Registration rights agreement [Member]	12 Months Ended
	Dec. 31, 2017USD ($)$ / underwritten_offeringunderwritten_offering
Related Party Transaction [Line Items]
Number of underwritten offerings, maximum, during 12-month period following shelf effective date | underwritten_offering	2
Primary shares cutback value, minimum | $	$ 25,000,000
Payments for fees and registration per underwritten offering, maximum (in dollars per offering) | $ / underwritten_offering	25,000
Certain persons receiving common stock or operating partnership units in formation transactions [Member]
Related Party Transaction [Line Items]
Registrable shares market value, minimum | $	$ 150,000,000
Number of underwritten offerings, maximum | underwritten_offering	4

Related Party Transactions - O

Related Party Transactions - Other (Details)	1 Months Ended	12 Months Ended
	Aug. 31, 2016ft²property	Dec. 31, 2017USD ($)ft²director	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jul. 31, 2016ft²property
Related Party Transaction [Line Items]
Area of real estate property (in sqft) | ft²		10,100,000
Number of directors (in directors) | director		1
Affiliated Entity [Member] | Leased space rental [Member]
Related Party Transaction [Line Items]
Revenue from related parties			$ 200,000	$ 200,000
Area of real estate property (in sqft) | ft²					3,074
Number of properties (property) | property					1
Affiliated Entity [Member] | Annualized rent revenue [Member]
Related Party Transaction [Line Items]
Revenue from related parties		$ 5,800,000	5,700,000
Undivided Interest [Member]
Related Party Transaction [Line Items]
Area of real estate property (in sqft) | ft²	5,351				647
Chairman emeritus [Member] | Leased space rental [Member]
Related Party Transaction [Line Items]
Number of properties (property) | property	1
Lease cancellation, period of notice	90 days
Percentage of lease space occupied by Chairman emeritus and employee	15.00%
Revenue from related parties, net of payment for pro rata share of leased space		$ 400,000	100,000
Chairman emeritus [Member] | Purchase of miscellaneous furniture and artwork [Member]
Related Party Transaction [Line Items]
Revenue from related parties			$ 23,300

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Increase in income tax expense	$ 400
Decrease in deferred tax asset	400
Current federal tax	(3,923)	$ (3,632)	$ (2,714)
Current state tax	(2,304)	(2,055)	(1,502)
Total current	(6,227)	(5,687)	(4,216)
Deferred federal tax	(446)	(291)	169
Deferred state tax	0	(168)	98
Total deferred	(446)	(459)	267
Income tax expense	(6,673)	(6,146)	(3,949)
Federal tax expense at 34% statutory rate	(4,684)	(4,629)	(3,003)
State income taxes, net of federal benefit	(1,543)	(1,517)	(946)
Corporate income tax rate adjustment	$ (446)	$ 0	$ 0
Effective income tax rate, percent	48.50%	44.80%	44.70%
Federal statutory income tax rate	34.00%	34.00%	34.00%

Income Taxes - Schedule of Def

Income Taxes - Schedule of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Deferred revenue on unredeemed observatory admission ticket sales	$ 1,395	$ 198	$ 267

Segment Reporting - Reportable

Segment Reporting - Reportable Segments (Details)	12 Months Ended
	Dec. 31, 2017segment
Segment Reporting [Abstract]
Number of reportable segments (segment)	2

Segment Reporting - Segment Re

Segment Reporting - Segment Revenue and Profit or Loss Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Revenue and Profit or Loss from Segments to Consolidated [Line Items]
Rental revenue													$ 483,944	$ 460,653	$ 447,784
Intercompany rental revenue													0	0	0
Tenant expense reimbursement													73,679	73,459	79,516
Observatory revenue													127,118	124,814	112,172
Construction revenue													0	0	1,981
Third-party management and other fees													1,400	1,766	2,133
Other revenue and fees													26,327	17,308	14,048
Total revenues	$ 183,070	$ 187,320	$ 177,124	$ 164,954	$ 179,263	$ 175,848	$ 165,815	$ 157,074	$ 165,200	$ 175,779	$ 164,773	$ 151,882	712,468	678,000	657,634
Property operating expenses													163,531	153,850	158,638
Intercompany rent expense													0	0	0
Ground rent expenses													9,326	9,326	9,326
General and administrative expenses													50,315	49,078	38,073
Observatory expenses													30,275	29,833	32,174
Construction expenses													0	0	3,222
Real estate taxes													102,466	96,061	93,165
Acquisition expenses													0	98	193
Depreciation and amortization													160,710	155,211	171,474
Total operating expenses													516,623	493,457	506,265
Total operating income (loss)	50,964	56,781	51,434	36,666	52,651	53,586	44,192	34,114	37,230	45,343	45,039	23,757	195,845	184,543	151,369
Income tax expense													(68,473)	(70,595)	(65,743)
Loss on early extinguishment of debt													(2,157)	(552)	(1,749)
Loss from derivative financial instruments													(289)	0	0
Income before income taxes													124,926	113,396	83,877
Income tax expense													(6,673)	(6,146)	(3,949)
Net income	32,260	$ 35,489	$ 31,359	$ 19,145	33,008	$ 32,897	$ 24,640	$ 16,705	19,370	$ 26,085	$ 26,585	$ 7,888	118,253	107,250	79,928
Segment assets	3,931,347				3,890,953				3,300,650				3,931,347	3,890,953	3,300,650
Expenditures for segment assets													228,162	197,680	156,754
Intersegment Eliminations [Member]
Reconciliation of Revenue and Profit or Loss from Segments to Consolidated [Line Items]
Rental revenue													0	0	0
Intercompany rental revenue													(77,646)	(75,658)	(68,255)
Tenant expense reimbursement													0	0	0
Observatory revenue													0	0	0
Construction revenue															(3,715)
Third-party management and other fees													0	0	0
Other revenue and fees													0	0	0
Total revenues													(77,646)	(75,658)	(71,970)
Property operating expenses													0	0	0
Intercompany rent expense													(77,646)	(75,658)	(68,255)
Ground rent expenses													0	0	0
General and administrative expenses													0	0	0
Observatory expenses													0	0	0
Construction expenses															(3,317)
Real estate taxes													0	0	0
Acquisition expenses														0	0
Depreciation and amortization													0	0	0
Total operating expenses													(77,646)	(75,658)	(71,572)
Total operating income (loss)													0	0	(398)
Income tax expense													0	0	0
Loss on early extinguishment of debt													0	0
Loss from derivative financial instruments													0
Income before income taxes													0	0	(398)
Income tax expense													0	0	0
Net income													0	0	(398)
Segment assets	0				0				0				0	0	0
Expenditures for segment assets													0	0	0
Real Estate [Member] | Operating Segments [Member]
Reconciliation of Revenue and Profit or Loss from Segments to Consolidated [Line Items]
Rental revenue													483,944	460,653	447,784
Intercompany rental revenue													77,646	75,658	68,255
Tenant expense reimbursement													73,679	73,459	79,516
Observatory revenue													0	0	0
Construction revenue															0
Third-party management and other fees													1,400	1,766	2,133
Other revenue and fees													26,327	17,293	14,048
Total revenues													662,996	628,829	611,736
Property operating expenses													163,531	153,850	158,638
Intercompany rent expense													0	0	0
Ground rent expenses													9,326	9,326	9,326
General and administrative expenses													50,315	49,078	38,073
Observatory expenses													0	0	0
Construction expenses															0
Real estate taxes													102,466	96,061	93,165
Acquisition expenses														98	193
Depreciation and amortization													160,630	154,817	171,035
Total operating expenses													486,268	463,230	470,430
Total operating income (loss)													176,728	165,599	141,306
Income tax expense													(68,473)	(70,595)	(65,743)
Loss on early extinguishment of debt													(2,157)	(552)	(1,749)
Loss from derivative financial instruments													(289)
Income before income taxes													105,809	94,452	73,814
Income tax expense													(1,306)	(1,361)	(1,498)
Net income													104,503	93,091	72,316
Segment assets	3,670,907				3,641,844				3,058,250				3,670,907	3,641,844	3,058,250
Expenditures for segment assets													191,541	197,680	156,543
Observatory, Segment [Member] | Operating Segments [Member]
Reconciliation of Revenue and Profit or Loss from Segments to Consolidated [Line Items]
Rental revenue													0	0	0
Intercompany rental revenue													0	0	0
Tenant expense reimbursement													0	0	0
Observatory revenue													127,118	124,814	112,172
Construction revenue															0
Third-party management and other fees													0	0	0
Other revenue and fees													0	15	0
Total revenues													127,118	124,829	112,172
Property operating expenses													0	0	0
Intercompany rent expense													77,646	75,658	68,255
Ground rent expenses													0	0	0
General and administrative expenses													0	0	0
Observatory expenses													30,275	29,833	32,174
Construction expenses															0
Real estate taxes													0	0	0
Acquisition expenses														0	0
Depreciation and amortization													80	394	338
Total operating expenses													108,001	105,885	100,767
Total operating income (loss)													19,117	18,944	11,405
Income tax expense													0	0	0
Loss on early extinguishment of debt													0	0
Loss from derivative financial instruments													0
Income before income taxes													19,117	18,944	11,405
Income tax expense													(5,367)	(4,785)	(2,791)
Net income													13,750	14,159	8,614
Segment assets	$ 260,440				$ 249,109				241,511				260,440	249,109	241,511
Expenditures for segment assets													$ 36,621	$ 0	211
Other [Member] | Operating Segments [Member]
Reconciliation of Revenue and Profit or Loss from Segments to Consolidated [Line Items]
Rental revenue															0
Intercompany rental revenue															0
Tenant expense reimbursement															0
Observatory revenue															0
Construction revenue															5,696
Third-party management and other fees															0
Other revenue and fees															0
Total revenues															5,696
Property operating expenses															0
Intercompany rent expense															0
Ground rent expenses															0
General and administrative expenses															0
Observatory expenses															0
Construction expenses															6,539
Real estate taxes															0
Acquisition expenses															0
Depreciation and amortization															101
Total operating expenses															6,640
Total operating income (loss)															(944)
Income tax expense															0
Income before income taxes															(944)
Income tax expense															340
Net income															(604)
Segment assets									$ 889						889
Expenditures for segment assets															$ 0

Summary of Quarterly Financia72

Summary of Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 183,070	$ 187,320	$ 177,124	$ 164,954	$ 179,263	$ 175,848	$ 165,815	$ 157,074	$ 165,200	$ 175,779	$ 164,773	$ 151,882	$ 712,468	$ 678,000	$ 657,634
Operating income	50,964	56,781	51,434	36,666	52,651	53,586	44,192	34,114	37,230	45,343	45,039	23,757	195,845	184,543	151,369
Net income	32,260	35,489	31,359	19,145	33,008	32,897	24,640	16,705	19,370	26,085	26,585	7,888	$ 118,253	$ 107,250	$ 79,928
Net income attributable to common stockholders	$ 17,272	$ 18,806	$ 16,584	$ 9,985	$ 16,966	$ 15,973	$ 11,089	$ 7,428	$ 8,252	$ 11,220	$ 11,120	$ 3,138
Basic and diluted net income per share attributable to common stockholders (USD per share)	$ 0.11	$ 0.12	$ 0.10	$ 0.06	$ 0.11	$ 0.12	$ 0.09	$ 0.06	$ 0.07	$ 0.10	$ 0.10	$ 0.03

Schedule II - Valuation and Q73

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	$ 3,723	$ 3,037	$ 1,847
Additions Charged Against Operations	(1,650)	908	1,298
Uncollectible Accounts Written-Off	(466)	(222)	(108)
Balance at End of Year	$ 1,607	$ 3,723	$ 3,037

Schedule III - Real Estate an74

Schedule III - Real Estate and Accumulated Depreciation - Schedule of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 717,164
Initial Cost to the Company
Land	199,287
Building & Improvements	918,018
Cost Capitalized Subsequent to Acquisition
Improvements	1,550,350
Gross Amount at which Carried
Land	209,182
Buildings & Improvements	2,458,473
Total	2,667,655	$ 2,458,629	$ 2,276,330	$ 2,139,863
Accumulated Depreciation	(656,900)	$ (556,546)	$ (465,584)	$ (377,552)
111 West 33rd Street, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	84,085
Initial Cost to the Company
Land	13,630
Building & Improvements	244,461
Cost Capitalized Subsequent to Acquisition
Improvements	76,316
Gross Amount at which Carried
Land	13,630
Buildings & Improvements	320,777
Total	334,407
Accumulated Depreciation	(31,591)
1400 Broadway [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	76,085
Initial Cost to the Company
Land	0
Building & Improvements	96,338
Cost Capitalized Subsequent to Acquisition
Improvements	28,738
Gross Amount at which Carried
Land	0
Buildings & Improvements	125,076
Total	125,076
Accumulated Depreciation	(27,287)
1333 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	66,590
Initial Cost to the Company
Land	91,435
Building & Improvements	120,190
Cost Capitalized Subsequent to Acquisition
Improvements	6,143
Gross Amount at which Carried
Land	91,435
Buildings & Improvements	126,333
Total	217,768
Accumulated Depreciation	(18,481)
1350 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	37,410
Initial Cost to the Company
Land	0
Building & Improvements	102,518
Cost Capitalized Subsequent to Acquisition
Improvements	21,601
Gross Amount at which Carried
Land	0
Buildings & Improvements	124,119
Total	124,119
Accumulated Depreciation	(19,330)
250 West 57th Street, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	2,117
Building & Improvements	5,041
Cost Capitalized Subsequent to Acquisition
Improvements	113,414
Gross Amount at which Carried
Land	2,117
Buildings & Improvements	118,455
Total	120,572
Accumulated Depreciation	(32,729)
501 Seventh Avenue, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	1,100
Building & Improvements	2,600
Cost Capitalized Subsequent to Acquisition
Improvements	92,032
Gross Amount at which Carried
Land	1,100
Buildings & Improvements	94,632
Total	95,732
Accumulated Depreciation	(39,550)
1359 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	1,233
Building & Improvements	1,809
Cost Capitalized Subsequent to Acquisition
Improvements	55,853
Gross Amount at which Carried
Land	1,233
Buildings & Improvements	57,662
Total	58,895
Accumulated Depreciation	(24,867)
350 Fifth Avenue (Empire State Building), New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	21,551
Building & Improvements	38,934
Cost Capitalized Subsequent to Acquisition
Improvements	803,025
Gross Amount at which Carried
Land	21,551
Buildings & Improvements	841,959
Total	863,510
Accumulated Depreciation	(174,484)
One Grand Central Place, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	7,240
Building & Improvements	17,490
Cost Capitalized Subsequent to Acquisition
Improvements	216,947
Gross Amount at which Carried
Land	7,222
Buildings & Improvements	234,455
Total	241,677
Accumulated Depreciation	(98,280)
First Stamford Place, Stamford, CT [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	178,378
Initial Cost to the Company
Land	22,952
Building & Improvements	122,739
Cost Capitalized Subsequent to Acquisition
Improvements	53,718
Gross Amount at which Carried
Land	24,862
Buildings & Improvements	174,547
Total	199,409
Accumulated Depreciation	(76,114)
One Station Place, Stamford, CT (Metro Center) [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	93,606
Initial Cost to the Company
Land	5,313
Building & Improvements	28,602
Cost Capitalized Subsequent to Acquisition
Improvements	13,489
Gross Amount at which Carried
Land	5,313
Buildings & Improvements	42,091
Total	47,404
Accumulated Depreciation	(29,225)
383 Main Avenue, Norwalk, CT [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	29,572
Initial Cost to the Company
Land	2,262
Building & Improvements	12,820
Cost Capitalized Subsequent to Acquisition
Improvements	17,534
Gross Amount at which Carried
Land	2,262
Buildings & Improvements	30,354
Total	32,616
Accumulated Depreciation	(11,933)
500 Mamaroneck Avenue, Harrison, NY [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	4,571
Building & Improvements	25,915
Cost Capitalized Subsequent to Acquisition
Improvements	22,393
Gross Amount at which Carried
Land	4,571
Buildings & Improvements	48,308
Total	52,879
Accumulated Depreciation	(21,928)
10 Bank Street, White Plains, NY [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	34,092
Initial Cost to the Company
Land	5,612
Building & Improvements	31,803
Cost Capitalized Subsequent to Acquisition
Improvements	17,042
Gross Amount at which Carried
Land	5,612
Buildings & Improvements	48,845
Total	54,457
Accumulated Depreciation	(19,441)
10 Union Square, New York, NY [Member] | Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	48,966
Initial Cost to the Company
Land	5,003
Building & Improvements	12,866
Cost Capitalized Subsequent to Acquisition
Improvements	1,787
Gross Amount at which Carried
Land	5,003
Buildings & Improvements	14,653
Total	19,656
Accumulated Depreciation	(7,359)
1542 Third Avenue, New York, NY [Member] | Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	29,384
Initial Cost to the Company
Land	2,239
Building & Improvements	15,266
Cost Capitalized Subsequent to Acquisition
Improvements	424
Gross Amount at which Carried
Land	2,239
Buildings & Improvements	15,690
Total	17,929
Accumulated Depreciation	(7,347)
1010 Third Avenue, New York, NY and 77 West 55th Street, New York, NY [Member] | Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	38,996
Initial Cost to the Company
Land	4,462
Building & Improvements	15,817
Cost Capitalized Subsequent to Acquisition
Improvements	783
Gross Amount at which Carried
Land	4,462
Buildings & Improvements	16,600
Total	21,062
Accumulated Depreciation	(8,166)
69-97 Main Street, Westport, CT [Member] | Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	2,782
Building & Improvements	15,766
Cost Capitalized Subsequent to Acquisition
Improvements	943
Gross Amount at which Carried
Land	2,782
Buildings & Improvements	16,709
Total	19,491
Accumulated Depreciation	(6,679)
103-107 Main Street, Westport, CT [Member] | Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	1,243
Building & Improvements	7,043
Cost Capitalized Subsequent to Acquisition
Improvements	182
Gross Amount at which Carried
Land	1,260
Buildings & Improvements	7,208
Total	8,468
Accumulated Depreciation	(2,109)
Property for development at the Transportation Hub, Stamford, CT [Member] | Land [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land	4,542
Building & Improvements	0
Cost Capitalized Subsequent to Acquisition
Improvements	7,986
Gross Amount at which Carried
Land	12,528
Buildings & Improvements	0
Total	12,528
Accumulated Depreciation	$ 0

Schedule III - Real Estate an75

Schedule III - Real Estate and Accumulated Depreciation - Reconciliation of Investment Properties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of year	$ 2,458,629	$ 2,276,330	$ 2,139,863
Acquisition of new properties	0	0	0
Improvements	228,162	197,680	156,754
Disposals	(19,136)	(15,381)	(20,287)
Balance, end of year	2,667,655	$ 2,458,629	$ 2,276,330
Aggregate cost of investment properties for federal income tax purpose	$ 2,305,283

Schedule III - Real Estate an76

Schedule III - Real Estate and Accumulated Depreciation - Reconciliation of Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of year	$ 556,546	$ 465,584	$ 377,552
Depreciation expense	119,490	106,343	108,319
Disposals	(19,136)	(15,381)	(20,287)
Balance, end of year	$ 656,900	$ 556,546	$ 465,584

Schedule III - Real Estate an77

Schedule III - Real Estate and Accumulated Depreciation - Schedule of Estimated Useful Lives of Investment Properties (Details)	12 Months Ended
	Dec. 31, 2017
Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated original useful lives	39 years
Building Improvements [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated original useful lives	39 years